Plz read and tell me what you think

So yes my man has cheated on me. And yes like a dumb ass I did take him (due to the fact it's been years and he has show me to love like no other) but he he did cheat idk why still till this day. So any way the girl that he cheated on me with lives down stairs from us (we live with his sister for the time being) any way his sister like to chill with this girl and just have her hanging around the house but let me know if I'm wrong for not wanting to stay there any more like could can you image after a long day at work U walk in and the 1st face you see is the girl who help your man cheat in U?? Please help I don't what to do or how to talk to him