Even if you ere thinking of something being possible between you and the young lady from work, leave it alone. she said she was in a relationship, having trouble, but still in a relationship. You are still married, no divorce, so you know what that would be if you did take up with this girl? Adultery does not make a good revenge against adultery. Just sayin'.
Having a drink with her as friends in a public place is fine, I guess. If your nephew reports backs to your W, then hey, it will give your W something to think about as in someone else seems to be very interested in what she didn't want anymore. And it could make her think she may have to rethink her plans. Maybe. Just play it cool, if your W says something, just say it's a friend of yours and that's it. If she brings up her having to leave to get you to change, tell her life is great, and you feel so much better about yourself.
Just be careful with your W getting all friendly and stuff, don't let her sweet talk you into signing anything you will regret. Taking care of yourself financially will be taking care of those kiddos, too.