My boyfriend of 2 years cheats with a girl he's been seeing for 5+years

I had always suspected. He came clean about the cheating . And I asked the other woman and she also came clean . They've got history. I'm not hostile with her and she is welcomed at his home where I stay .I blame myself for making it like a party house for out mutual friends to meet up at and stuff . I pretend it doesn't bother me . When I asked her to leave one night I couldn't stand the thought of what they did he said she doesn't have to go anywhere . I don't get it though how he cheated with her and he talks the most shit about her the one he cheated with . They've been screwing around for years . He came clean. Everyone around us says he loves me. She hasn't came around since I asked her to leave . She only came around because ok don't judge me I invited her over and welcomed the gal with arms wide open. She loves him of course . And I sympathize for her. But she needs to get her shit together and realize he don't love her.