to expect my dd 14 to act a little more mature and help out with newborn

I think you've shot yourself in the foot with the title. Mumsnet thinks we should all be completely self sufficient woth our kids and never ask for any help. You'd get more sympathy if you'd asked if she should help with chores.

Yes she should by the way as she is 14!

Also my god I was out clubbing when I was 14 and going places independently for a while before that. She can surely manage the supermarket!

You asked the neighbour to go to the shop because you were tired? Were you that desperate it could wait for your dp to bring it home after work?

it would be nice if she wanted to be involved more. But she doesn’t.

She didn’t plan and have a baby, but the baby has caused disruption to her life (which it has if her mum is too exhausted to even go to the shop which must be close by if you wanted her to go) and she isn’t interested.

what would you do if she wasn’t there?

Was she doing stuff like going to the shops for you before you had the baby? If not yabu not expect her to have had a personality transplant and start being helpful. You should have enforced some chores regardless of whether or not you were having a baby.

I think you need to give her a lot of time to adjust. Presumably you managed without a 14 year old helping you last time you had a baby so you shouldn't be leaning on her to help this time, she may well choose to in her own time but I can imagine she has very mixed feelings about your decision to have another child. I know my mum chose to go to boarding school after her mum had a baby when she was 14.

No. Children are not there to do the donkey work because you chose to have another baby. Did you even ask her before getting pregnant.

This.
Do not 'have a massive go at her', you should be spending time with her one to one and talking to her about any worries she has, and reassuring her.

Also wondering if this is a half sibling and the 14 year old is also dealing with a stepdad in the house and generally feeling pushed out in favour of the shiny new family.

I actually do think it's fair to expect her to help by going to the shop or whatever.
I'm sure you help her with things all the time. I'd have little patience with a teenager embarrassed at the idea her parents have procreated again. But then I don't have a teenager myself so perhaps I'll adjust my thinking when I do.
But I expect my primary aged kids to help out and do what they can to make our household run as smoothly as possible.

She’s a teenager with all the hormone-induced angst that that brings. She’s probably feeling a bit jealous and vulnerable and you’re not helping her. Give her time and consideration and I’m sure she’ll up her game.

She should be doing her bit to help around the house anyway at 14. But as PPs have said, it must be a huge adjustment for her. She probably feels like not only is she being pushed out/replaced by a new baby but she is no longer being treated like your child. She probably needs extra care and a good chat with her mum, even though you'll have zero energy for that right now! Make sure she knows she's still your 'baby' too and she might be more willing to get involved?

OP, I disagree with all the above posters completely. Yes it's an adjustment but she needs to pull her socks up and pitch in. Nobody is entitled to be sibling free and she needs to grow up, adjust and yes help a little more. Even 5 year old s8blings help in small ways.
You're not expecting anything unreasonable. We need to expect far more resilience and sense of responsibility from our teens.

You have chosen to reproduce again at a time she would rather have you around to do fun mother-daughter stuff, help her with her GCSE options, take her out at weekends, not spend it sat at home exhausted, pushing a pram, changing nappies and breastfeeding. What’s the betting any summer holiday plans have been grossly limited by you being heavily pregnant too. Did you even consider her in this plan? No wonder she is pissed off.

Exactly this. Especially if she's been an only child for 14 years.

You chose to have a child. Not her.

She is still a kid.

She has ZERO responsibility towards her younger siblings.

It's awful that you're relying on her for anything more than she WANTS to do and if that's nothing then at 14 that's understandable.

Leave her alone. She's already dealing with the attention being directed at the baby.

She should not be expected to do more chores because you have had a baby. If they were pre existing chores/expectations then yes, but she should not be expected to suddenly do more.

You chose to have a baby and she may not be too happy about it.
She shouldn't be rude but I think you are expecting too much from a teenager who is dealing with a big adjustment.
Where is her/babys Dad in all this?

You can't see why she might be embarrassed given the big age gap and the notion that everyone knows her parents(?) still procreate?

Going to the shop for something non baby related, maybe but not expecting her to fetch and carry if you're occupied with the baby .

I feel like having a right go at her and telling her to "grow up you are nearly 15 for gods sake"

Well you are the gown up who decided to have this baby. Why don't you grow up? Have you even considered your 14 year oldest feelings?

Laughing at the "she's a child" post. She's also a sulky teen who should get her head out her arse and help her mum. You know like we all probably did.
At 12 I was doing the family washing sometimes because my mum worked full time and had a health condition that meant she had to stay in bed all weekend occasionally. Did I begrudge helping? no because we are all part of the same family and love each other.

She should love and respect you to want to help out regardless of who the df is!! I had a dc when my dd's were 8 and 9.. They learned how to make me a cuppa - their idea - to help me when I was sat bf their ds.. No half sibling crap in our house...

I think you are being alittle unreasonable, you have had a baby not your 14 year old. You should be looking to your husband for extra support not your 14 year old. Any help she gives you should be a bonus, not an expectation.