I'm going to cut ties with my friend who is cheating on her fiance.
Do you know for certain that she is cheating on her fiance?
Yes. I have seen it with my own eyes. She doesn't know anything about loyalty anymore.
If you believe what she is doing is wrong, then you have every right to end the relationship with her. It's expected to stay faithful to your partner when in a relationship. So, many people would not want a friend who cheats on their partner.
I feel like I can't forgive her for this. But I'm still going to spend time with her because I'm a charitable person.
There's nothing wrong with wanting to end a friendship over something like this. If you still spend time with her though, it may send her mixed signals that you want to remain friends. You may want to be more clear that your friendship is ending.