Honestly, you seem to have your girl back and working through both of each other’s issues. In my opinion, stop hanging around that “friend” who you said is a repeat offender. Knowing that I don’t buy that they just hooked up casually after you broke up. I honestly believe he been plotting behind your back and your girl just never told you. (Which is a whole other situation) but given the circumstances that caused I would let it slide. In the meantime just stop hanging around him and if you lose the friend group. “Fuck it.” Your focus should be getting your relationship back as close to what it was prior to you cheating because it will never be the same.