Do you think that I should tell someone that wants to be friends that I've slept with her ex?
Why did you sleep with her ex?
There is this mysterious attraction between me and him
It's perfectly fine to confide in a friend about what goes on in your bedroom, but you may want to make sure that pal isn't the town gossip. Rumors spread fast and misinformation could lead you to have a reputation you don't want.
I'm going to tell her that I want to be friends again.
Making an attempt to fix your friendship is great. You should always be honest in your friendships so that you don't lose trust.