Our sons are growing up together, I just want to be friends.

I was really grossed out when I found out my fiancé slept with this girl (known to get around) a few months before we started dating. Well, when my fiancé slept with her once and told her it wasn't going anywhere she tried to kill herself and was in an institution for 4 months. I also used to take dance with her and she's my cousins best friend. My cousin says she's come a long way mentally though. While I was pregnant with our first she announced a couple months later that she's pregnant and it's a boy. I was so scared it was my fiancé's but the timing didn't add up. She claims she was black out drunk (at 19... We've all been there) Well she used to follow us around church and stare at me with a death stare... I started to like stalk this girls IG and FB since I got a notification on IG that she liked an old pic but then she Unliked it. Clearly she checking my pages too right? Childish of me I know... But then I also started to notice that we like the same stuff, dress similarly, love to sing, and besides, we used to be cool when we had dance together... And I realized, this girl is actually pretty cool... Well, our sons are in the same Sunday school class and her son is the sweetest ever. I absolutely love how he always wants me to pick him up but I can't. She's never around him. She's always with her friends or her new BF. Something told me I needed to apologize for having been so "jealous" with what she and my fiancé had in the past and that I hope some day we all can move on from the past since we see each other a lot, our boys are growing up together, and she is always around my cousin and I hate that I can't see my cousin when I want just Bc she is at her house all the time and she doesn't want to be around me (my cousin tries to convince her to let me hang with them and she won't). Basically she's my "enemy" but really, after everything, I just want to be her friend. We could be having mommy and son play dates together and sing together in church if she would just like me :( I can't make her be my friend but I'm hoping one day she can forgive me for having ill thoughts towards her in the past and not hold the fact that my fiancé is who he is against me. This was such a long post but I had to tell someone how I told her I was sorry and I wish we could be friends.