I am very possessive of my children. They are the center of my universe and when I first read your post I thought "OMG what is wrong with this woman!!!! Who does she think she is!!!!" But then I thought about it for a minute; what would I do if I were in a serious relationship with a man with children. And I would be that woman. I would make that child just as much a part of my life as I possibly could. And I would also do everything within my power to help him make sure that he utilized his rights as a father to the fullest extent possible. I hope that I would respect the child's mother enough to establish a courteous relationship with her as well. But who knows what stories she's heard about you from your ex. Divorce brings out the ugly in a lot of people.

The first thing I would do is speak to her directly and establish boundaries. Let her know that you appreciate the positive influence in your child's life, but that when it is your turn to have custody, she must respect your wishes/decisions. Because after all, the more people that your son has that love him and look out for him the better off he'll be. If your husband has decided to become a better father (whether it is because of her or not) that will only benefit your son in the long run. BUT and this is a big BUT, let her know that if she isn't willing to discuss this as an adult, she doesn't have a dog in the fight. She has no legal or moral right to discuss anything regarding your child. I do not understand the PTA thing, but you don't have to have a child in school to be a member. BUT you can prevent the school from giving her access to your son with a simple phone call. Almost married does not count.

If that doesn't work, I'd speak to the ex. Let him know that you understand that this woman is now a part of your son's life but you are the child's mother and currently this woman is a guest in your child's life. (I may be archaic but in my own personal opinion she should not have been introduced to the boy until there was a ring on her finger and a deposit on the hall.)

In the meantime, do document any negative actions (i.e. fights at the baseball game) so that if/when this becomes a family court issue it doesn't sound like sour grapes.

Please let us know how it turns out.