*FML.
A bowl of trifle could have gathered this concept by now.
It does not matter what MN thinks about their choices. It does not matter what you think about their choices. It does not matter what I think about their choices.
They have made their choice. Six years ago, and maintaining that choice now. That's not up for debate. The issue is OP's reaction to them maintaining their choice and threats of divorce over it. How she is up in arms if anyone else treat the DDs differently, despite doing exactly that herself by saving for only one of her children.
People pointing out, she was well aware of this from day one, so has no right to tantrum now, are seemingly met with irrelevant hallmark card shite about how anyone can be a dad but it takes a man to be a father...which is a) lovely and b) makes no bloody difference to the fact OP knew they didn't see her child as family from day one. And that's what is relevant. Not what Sue from accounts would do now. That OP knew the position, put her child in it regardless, and wants to make things somehow their fault for maintaining what they always said they would do. And let's not forget OP ignoring the actual paternal family and all the day to day stuff, food, housing, clothes, parenting that DH is providing in their place. No acknowledgement of that, at all.
And as for "well you could say the DH didn't know what he signed up for" is just utter stupidity. Because it's beyond obvious he's doing exactly what he "signed up" for. OP however, agreed to marriage and another child knowing her existing DD was not accepted as their own, but did it anyway and thought she'd talk them round. She's attempted that over this wedding issue, with threats of divorce. And that threat has resulted in her getting one wedding invite, and it categorically spelt out to her, that they never promised to take her on as her own, and will not be via school fees, savings or inheritance, but they will be doing so for their DD/granddaughter/niece, with or without her approval. I think she's realising that she either accepts this, or she is welcome to leave and divorce because their priority is and will always be their own family, DH and his DD. She wasn't expecting that, and her "trump" divorce card that she thought would shock everyone into her court, appears to have had zero effect now she's played it.
Banging on about "well, I'd never distinguish between them" is lovely. And completely irrelevant. They do. The thread is about that being the fact of the matter, so where does OP go from here.*
Where does OP say she knew her DH would not accept DD as his own?
And that the OP knew the family would not?
Seriously I can't see it. @WillYouPutYourCoatOn
I can only see OP saying that she only expected her DD to be treated well and on a par to any other children.
Signed
A trifle