It's a MIL one - stop me before I say something I'll regret

You're not being unreasonable, OP. She booked with you first, and she should have honoured that commitment. There'll be other nativity plays, and she can always see a video. It may not the same, but she was already committed elsewhere.

When you said that your DD pales in comparison to your SIL's child (in MIL's eyes)...I have seen this dynamic play out in my own family, and it's not pretty. My dad's mum had two sons and a daughter. Her favourite GC, by far, was her daughter's daughter. As my dad said to me, you'll never compete with the daughter's daughter. Sounds like something similar is going on here.

Your MIL is wrong to play favourites and wrong to bail on one branch of the family for another. That's a surefire way to spread family discord. Doesn't anyone with half a brain know that you don't play favourites and you honour whichever commitment was made first, except in extenuating circumstances? (e.g. If my friend and I had planned to slope off to the pub for a swift half, I doubt she's mind me cancelling if I got invited to a ball.)

Your MIL is silly and immature. I'm sorry.

There's nothing you can do with people like that, who are self-centred and bad-mannered. I agree with your DH. Rise above it and have a lovely time without them.

She is probably trying to keep everyone happy but she has to realise she can’t be in two places at once.

I would politely let her know you are hurt by her decision.

Is the SIL a madam?

With respect (and I genuinely don’t mean this harshly), are you projecting some of your stuff here? You seem really over- invested in trying to create a strong bond between MIL and your DD and to level this out as being equal with your MILs relationship with DGS.
My MIL massively favours her daughter’s children to our kids; they can do no wrong! Her daughter is the best mother in her eyes and I am a bit rubbish! She always shares pics and videos of her other grandkids and it is annoying! I think that this might be a ‘thing’; that some parents feel more connected when it’s their daughter (rather than their daughter in law) who has had the baby.
if I were you I would try to chill out and step back. Invest your energy elsewhere! Your DD will not feel second best if she feels valued by you and her daddy.

And the grandson is 3.5 years old? Not a school nativity?

It's a nursery nativity?

Oh now ive heard it all

HUGE eye roll

Well, if she had as much as a natural relationship with the poster and the siblings she wouldn’t be seeing more of one set of DGC she?

Sure, but they already went to his nativity last year… so it’s not exactly a huge moment… also the kid is probably playing sheep number 3. Not sure these are memories of a lifetime….

What? Their Grandchild?

Of course they can miss it

I really don’t understand the posters saying she’s trying to do both and she’s being nice!

She sat down and planned a day full of activities (and let the OP pay for them!) which included seeing Santa with her granddaughter, probably a nice lunch afterwards, and has cancelled those to go to her grandson’s nativity play.

The highlight of the trip is the visit to see Santa as this will be the first time that OP's DD has seen him. This is an activity that was discussed with OP's MIL and FIL before OP booked and paid for it and they were all looking forward to it.

This event will take place while MIL is at the Nativity. The activity will go ahead but MIL and FIL won't be there to see their grand-daughter's delight at seeing Santa for the first time. They have already seen their grandson's Nativity last year. They are wasting OP's money and disappointing their grand-daughter.

OP if you don't mind me asking, how can you be certain your sil isn't making your mil feel guilty for not attending the nativity & do you disagree she should be persuading your mil to attend your trip for the whole duration. It's what I would do in this situation but to be fair you know them best.

We have a similar situation with my mother-in-law. We could plan the most lavish events for her but if his brother had a sniff of needing a tiny bit of assistance from them, she would drop everything and run. I agree with what everyone else has said in that you need to express your dissatisfaction to her. I had a psychologist who once said if you don’t throw your toys out of the pram every now and then, people think you’re a pushover and don’t respect you. To be honest you could just completely lose your s**t and see what she did. She’d have to come crawling back wouldn’t she?

Why doesn’t your mum have a “natural relationship” with your siblings?

So you assumed this rather than misunderstood? Because no where is this said

@thepariscrimefiles

I don’t think they are cancelling, I think they are planning to do both?

Is your sister available this year?

So would your mum cancel a planned meet up/event with one of your siblings partners and their child/children if you invited her to something after them?

I haven’t misunderstood. I know the poster wrote that their mother has a more natural relationship with them than with their DDIL or their siblings partners. But what about their siblings? Why doesn’t their mother have a more natural relationship with them? Why can’t their mother see them and their children as much? It just plays into the trope that if you’re a mother of boys you need to get used to not seeing your DGC because they will be off with their other granny who they will have a “more natural” relationship with .

maybe you should reread this post @TheFairyCaravan you have misunderstood

Why doesn’t your mum have a “natural relationship” with your siblings? Don’t say it’s because they’re boys, because that’s utterly ridiculous and complete bollocks. And if a result of your mother having a more “natural relationship” 🙄 with you that she prioritises your DC over her other DGC then it makes her not a very nice person imo.

This is the crux of it all. They made a commitment to you and your family and jointly selected activities for the one major day you are there for the whole day.

Now she’s saying something has come up that she’d prefer to attend on that one whole day and is prioritising the invitation that was issued after yours was accepted and agreed upon. It’s bad behaviour. She should honour your break that you’ve paid for.

I really would be tempted to say this isn’t going to work and cancel their trip.

Please say to your DH that if MIL says"Oh, next time" in an attempt to smooth things, he's to say "No, we're not going to plan another family holiday like this - this has been really disappointing, so we don't want to try and plan another one". That might bring it home to her.

Do people actually give a shit about a nursery nativity? Sounds like a chore to me tbh. I'd be pissed off with MIL too.