+1The only two real reasons she could want you involved with the existence of the new baby is that 1) she wants to rub your face in it or 2) she wants to make sure you are emotionally invested and will be a support to HER if and when the whole thing goes way South on her.
Assuming it is not Choice #1, then you need to be prepared for Choice #2, the day when she expects emotional support from you divorce-or-not. Women are often masterful at keeping all their options open and never totally closing down a useful avenue of potential support.
Your problem is to decide how you are going to react on that day when she shows up crying over the decisions she has made the last couple of years and expects your support.
I only say this because it sounds like this potentially is laying the groundwork for a lot of future drama for you. Divorce yourself--legally, financially, emotionally, and morally from the whole thing. Getting distance now will make you better prepared to handle potential drama down the road.
Amen