Advice please. Sorry there's a whole story kinda

Lauren
I have these two bff's for 6 years now. Last year I became friends with a guy and started to like him. I introduced him to these two friends and one grew feeling too. The other friend kinda did too but not that much. I eventually started dating him. 6 months and the then we broke up. It was a fun relationship but he grew feelings for my friend that had feelings for him (let's name her Sara) and said that I deserved better. During our relationship Sara got a bf ( a rocky relationship  At that). My ex told her about it blah blah. Sad I was in a sad state she told me that she wouldn't date him...
I have a new by who is super awesome 👌🏼😁😍. Recently she Sara asked me if she could date my ex.... I said no I don't feel ok with that. She got mad and we had a back and forth about it. I told her about the girl code but she follows it subjectively. In the end she told me that she wouldn't go for him. 
I do feel betrayed that our friend has come to this. Should I trust her and keep her as a friend. But recently she we both have been distancing ourselves (poor second bff we share) idk what to do. Everyone says fuck her she's not worth it. Idk anymore. I see her and I just feel they haPPyy day turn ugh . Help please.