Your divorce arrangements and provision for your child are NONE of your new partners business. REGARDLESS of how you got together.
It wasn't her marriage, not her child either.
The csa guideline is a MINIMUM amount considered acceptable. It sounds to me you have a fair idea of the costs of raising your child (which include housing, heating, water, transport, clothes, shoes, food, toiletries, books & toys. Currently nursery fees but even once at school costs tot up - uniform inc gym gear, equipment, school trips...and those are the BASICS - you know what these things cost while you were with ex, are you REALLY paying 50% of all this even with the 'little extra'? Highly doubtful).
As one of your child's parents morally (if not legally - personally I think it should be made legally) at least you are responsible for 50% of costs.
If both you and your ex work and your child needs to be in full time/wrap around care as a result, I'd argue you're also responsible for 50% of that.
If it's bothering your new partner THAT much
A she needs to grow the fuck up! Does she have DC?
B she should have thought about that BEFORE getting involved with someone with DC. And that would apply if you'd been single when you met too.
C she needs to realise it is NOT your role to provide for her. She's a grown ass adult she needs to provide for herself or if there's a valid reason she can't (eg disability) she needs to organise support for herself AND either way she needs to learn to live within her means.
Your new partner sounds immature, selfish and jealous of your child.
You need to grow up a bit too - you're not 'trapped' your own choices as an adult got you where you are now.
"My ex earns more than me" in terms of your responsibility to your daughter that's irrelevant.
"but am I being blinded by a sense of guilt and misplaced loyalty?" Absolutely not! You DO have a loyalty to your daughter as a parent and to your ex as a co-parent - if new partner can't hack that she needs to sod of!!
"Dump her. She is going to fuck up your childs life. She will make her resentment very clear." Yep!
Of course your marriage wasn't functioning! You were putting your energies & focus elsewhere. As pp said classic cheaters script.
"You don’t have to go back to your ex, but you do have to put your child first, and staying in this relationship isn’t doing that." 100% agree with this! I rather suspect too that if you have DC with her she'll get even worse and see it as taking money away from your older child. And...then I read new partner is pregnant! Shouldn't be surprised really, let me guess, she started this 'it's too much money' narrative after she got pregnant? She wants to push out your older child, emotionally, physically as well as financially. YOU don't have to let her.
Then you’d better set some firm boundaries right now - definitely!
And can I STRONGLY recommend you educate yourself on sex & contraception - or certainly better than your current knowledge, cos I suspect either your knowledge is poor, you have a lazy attitude to using it, or (and I'm not sure this isn't worse) both children were planned in terms of contraception, but you didn't think about your new partners attitude to your daughter and how another pregnancy would impact on that.
Hirples son sounds a damn site more mature and responsible that either you or your partner. Hirples your son sounds lovely, good on him.
"Bet when she's chasing you for maintenance in a year or two's time she won't think her child deserves the bare minimum."
Just what I was thinking! I'd lay odds there's no way she'd accept such treatment herself.
"Tell your partner that you will only contribute to your new child the amount that the older one gets." Excellent advice - borrowing for future similar threads! I wonder how many 2nd wives/partners would like that?
My dd is 17 and hasn't seen her father for several years. His choice (but I get the blame), his lack of effort in organising visits is the issue. He also never paid regular or full csa min maintenance. Deadbeat arse! He TRIED to claim at one point to dd that he WAS paying maintenance regularly in full - easy enough to prove otherwise on my bank statements.
Added to which in terms of his 2nd wife I have the reverse situation, she has actually been very supportive of my side of things, when they were first together she'd chivvy him into paying which would work occasionally, would chivvy him into making arrangements to see dd (she actually did the bulk of the organising but she can't put his leave applications in for him! Which he would always leave to the last minute and then they'd be turned down). Unfortunately now he doesn't even listen to her, hence he hasn't seen dd for years. I was the one left dealing with a heartbroken teen who truly believes her dad doesn't love her. So he doesn't even have the excuse of a difficult 2nd wife.
Dds relationship with her father is irreparably damaged, I'll be very surprised if they have any kind of relationship in the future. At this point she wants to visit to see her grandparents (very elderly and frail), half siblings and stepmum (who while she was the ow, as a stepmum has been spot on when she's had the chance). Do you want this to be you in 13 years op? Not seeing your daughter, her not wanting a relationship with you, her already deciding you'd barely be welcome at her wedding let alone be able to maybe walk her down the aisle? Because if you don't sort this now that's where this is headed.