To be upset by sister’s attitude

Put your tiny baby first and tell your DS that you will be unable to be her bridesmaid , what if one of the children are unwell on the day will you be happy leaving them to pander to your DS.
Best to tell her sooner than later, if she goes mad it's too bad.

There is 2 hours between the church and reception sorry that’s bonkers.
Honestly I bet the marriage lasts less than 2 years.
Im glad you are planning to push back, personally I’d attend the service and skip the reception since your family aren’t really welcome.

Am I right she said you knew when the wedding is going to be, in relation to your planned c?

Childbirth or planned caesareans happen when they happen.

If she was a rellie of mine, I might suggest she seek advice from her GP to get something to calm her down?

Your sister is insane. She’s so far unreasonable she’s off the scale. Stand down as bridesmaid and tell her either all 4 of you go to the wedding or none of you go.

You will need to put your child's needs first and it should go without saying that you cannot choose when your waters may break! Your sister sounds unbelievably selfish and none too bright, and mother no help at all - so you have to look after yourself. As others have suggested I'd withdraw from being bridesmaid as you just can't do it in the way she wants - then keep your options open about what you might do. Babies have a habit of being unpredictable!

Breastfeeding bridesmaid will upstage her. Everyone will be focused on your new baby... No. Actually people will be looking at the Bride and Groom. It really annoys me that people think members of the bridal party will steal the limelight.

If she wants you there, you will be there with baby. End of. That's the deal. She can take it -- or leave it.

I also don't understand child-free weddings. They are caused by weddings so theoretically as people marry or get older, they will have kids. Unless you all get married within a few months of each other there will be kids. I get cross seeing people who happen to be the first to have kids suffer. I'm sure she'll want HER kids at all future events and kick-off if they're not included.

I’d be telling her to stick her bizarre demands where the sun don’t shine, OP - as a pp wrote, you have your own family now and you’ll be only 10 weeks post-partum. You’ll always remember this ridiculous saga and the upset it’s causing you if you give in.
How the hell did she find some poor sod a guy to marry her? She must be a bloody nightmare to live with!!

Frankly this is batshit and you need to stand up to your sister , yes it’s her wedding day but it doesn’t give her the right to “demand” how you spend your time, leave your baby at home etc. I would suggest for everyone’s sanity you step down as bridesmaid now. After a c section and with a 10 week old baby there is no way you can manage all her demands which I sure will just get ever more ridiculous as the wedding gets closer. I’d suggest something along the lines of

“sorry Tabatha, but I don’t think I can live up to your ridiculously high expectations of what a bridesmaid will be doing for you. I will be managing a 10 week old baby and will have had major surgery myself which I will still be getting over. I think it’s best if I step back and you rely on your other bridesmaids who can give you the support you want and can make sure you have your special day”.

You have to decide who's more important, your sister or your baby and family.

Agree with above.

She is a complete bully.
Step down as bridesmaid.
What does the rest of your family think? Is there someone who can have a word with her.

The only very slight benefit of the doubt I would give her is that she just doesn't understand the demands of a new born ( and you have an older child too). Of course when she has her children, she will be a Pregzilla and a Mumzilla too.

Since her reaction is to huff and walk off - she expects you to run after her and try to sooth her. Don't do it. Let her walk. She will come back for a second round and you will have the great satisfaction of saying to her I tried to talk to you but you walked off as usual. Don't keep taking this on the chin. Be brave for your baby and yourself. Put that foot right down and show that you ain't budging. They will come to realise that you mean it - however much bad mouthing you have to put up with - let them. You know you are in the right.

Then you can’t be bridesmaid as you can’t go to the church. That would be crystal clear to me.

Oh dear. You need to put yourself first in this scenario. Yes the wedding day is about the bride and groom but that doesn’t not give the bride the right to demand people to revolve their lives around her or make ridiculous requests. You will have just had a baby, (the demands and recovery should be obvious to people) you have a big recovery ahead, just because it’s not your first doesn’t mean it’s easier. Adjusting to two can also be a lot to handle. She’s is a sister to you too and you would think she cares about you too. Leaving kids behind is one thing, but a newborn is harder and if you are not comfortable with that then you shouldn’t have to.
If she actually told you that you should have planed your trying around her wedding, that is where I would have stepped away and told her I’ll attend but I’m not going to be running around you.

With the church and reception 2 hours apart, I suspect a lot of the guests will opt for one or the other but not both.
I thought we were pushing it with reception being 30 minutes from the church!

OP Some people are narcissists. They are usually supported by enablers.
Narcissists don't benefit by changing.
Enablers fear the repercussions of standing up to a narcissist because narcissists tend to react badly when anyone stands up to them.
Narcissists have a huge sense of entitlement. Enablers inadvertently feed this enormous sense of entitlement.

Your sister sounds like a narcissist. Your mother and her boyfriend are flying monkeys and Enablers, probably in a vain attempt to keep the peace.
You sound like a scapegoat, a people pleaser.
You need to erect boundaries with narcissists and their flying monkeys or the damage they do goes onto affect your DC.
Please understand what a boundary is OP. A boundary is not telling someone they hurt your feelings or explaining to them how you feel expecting them to understand. This is simply expressing how you feel.
A boundary is making clear what you will or will not be doing and what the consequences will be if they don't accept the boundary.
In your sisters case, it goes something like this;
"Sister, I am stepping down as bridesmaid from today. Unfortunately I cannot prioritise bridesmaid duties now I've had my baby and I'm not prepared to compromise to the level you wish me to.
I am happy to attend the wedding service and I'm looking forward to seeing you get married.'

If she or anyone responds by revoking the invitation, or being abusive, simply respond by saying you're sorry they feel that way, but you have made your choice and you won't be changing your mind.

If your sister refuses to speak to you after that, count yourself and your children extremely fortunate that your sister has then done what it really sounds like you need to be doing, removing yourself from this toxic equation.
Your DC will thank you for escaping this toxic situation and will appreciate not being recruited as the next generation of flying monkeys.
You will find peace when you remove yourself from this dynamic.

Having such a huge distance from ceremony to reception is bonkers! What if there’s a big hold up and everyone gets stuck in traffic, the meal will be ruined- for someone so ott about their wedding this seems crazy. If I had a baby niece I would make them the star of the show at my wedding and get the most gorgeous outfit and photos- just saying… pop to the ceremony and then go and snuggle your baby

Wow!

I'd say I can do what I can but my baby will need me and she will be my priority. Do not leave your DH at home with the children, wtf. Weddings are family affairs. If she doesn't like that, the option is for her to find another bridesmaid.

2 hours from the ceremony to the reception?! That’s insane! Has she got many guests?

I'd have told her to shove her wedding up her arse the moment she made the comment about your waters breaking tbh. Who the hell does she think she is?!

You're having a baby. Stress and upset will be bad for both of you. I think you should either pull out now or develop some cast-iron boundaries - and stick to them.

If the church is 15 minutes from your house then go to the ceremony, but decline the rest of the day as you don't want to be away from your newborn.

This isn't about a wedding.

She's aware these are her neice and nephew right? She's entitled to be the center of her world... not yours

You are going to have to draw the line at some point. Up to you whether you do it before the wedding or after. But she is determined to dominate and abuse you. Your family isn’t “co dependent “ it is managing a highly narcissistic, abusive, person. She is rocking the boat every second and you all rush to stabilize it (that part is codependent). If you stop rushing around stabilizing the boat she will have to fall in the water and learn how to swim. Just get off the boat.

Your sister is clearly a narcissist. She is clearly making the wedding all about her, not about marrying the love of her life. She expected you to put trying to conceive on hold so the focus wasn’t taken away from her. The story about the cream jumper ( at a dress fitting !) is just wild. She has zero empathy and understanding for you.
Why is everyone accommodating her insane behaviour?
You and other family members should give her a reality check. You need to prioritise your mental health with this shit. As others have said, stand down as bridesmaid. Good luck 🤞

Do the other guests know about the 2 hour drive? Suspect there'll be some cancellations once they find out. I certainly wouldn't attend both venues.

I thought your DSis was just being over the top about the wedding but it sounds like that's her normal. Your family dynamics are worrying, a bit like you all have to present a united front, all so happy and close, even though you're all at odds with each other and no ones allowed to stand up for themselves or tell the truth. Frankly Op, if you say no to your Dsis and it turns into the family row of a lifetime they may not be a bad thing. Time for some honesty Op

You were wearing a cream jumper? She's a total nut case!!