I hooked my brother up with my BFF

Okay so my best friend is cool and she said she is tired of guys cheating on her and whatnot and my play brother was looking for a gf so I hooked them up over the summer. At first it was great but then my BFF started to hoe and she has like over 10 guys and at least 1 girl + my brother. I told him after a month or so tryin to get her to stop, he had a convo with her n she admitted to some of it (she don't know I told him). He refuse to dump her because he says that he loves her, he is letting her move in with her this semester and he is looking for a ring for cuz he wanna marry her after she grad high school( she's a sophomore and he's a junior) neither of them are virgins, she's fucking behind his back n he is completely faithful to her. I think I accidentally hooked my big brother up with a hoe. Help ! Please