I really hope my ex wife and ex girlfriend won't be friends
Why don't you want your ex-wife and ex-girlfriend to be friends?
They know each other so very well. I'm afraid if they become friends again it will be tough to keep some things secret.
You should not try to break up a friendship for your own benefit. Getting in the middle of a friendship will cause you to seem bitter with both of your exes.
What? I'm cheating on my wife with my girlfriend. I want them to dislike each other for my gain.
You sound like you are in a big mess. It might be best for everyone if you cut ties with both exes and keep your lives separate.