Do you know her previous last name?

It might work well, especially for your daughter (what else matters!), if you took the high road and sent them both a brief congratulatory note. You might consider adding on at the end how much you hope all of you can work together on the kids’ behalf. If you are comfortable, offer your e-mail address and, perhaps, you two can communicate about “kid stuff” in that way. What develops beyond that is really up to the both of you. Good luck!

I did remarry at one point and only my oldest child (already a grown married woman) called her step mother by her name. Otherwise she was “mum” to my children. I never told my children what to call their step, but calling her by her first name was never an option for my youngest. It might just be a Southern thing (although I’ve lived in many places out of the South), but I could never have dealt with my youngest calling an adult by simply their first name. My children were all closer to their step, and even though she and I went out separate ways, but not because of a bad marriage (she never wanted a divorce, but had to move back to Europe), they are still emotionally closer to her than their biological mother. Probably because their step was more of a mother to them.

Giving birth makes someone a mother, but not “mom”. Just as impregnating makes a father, but not a “dad”. Children will sort out who they feel close to…or not. Who they feel is a parent, and who is not. All I ever required was that my children show respect to their mother and their step. The rest they will sort out.