I feel that you had brought this person to your house to make a new friend which was a kind gesture, but you decided this wasn't the person you wanted to have a friendship with. Your wife had hit it off with this person and became friends. It makes you uncomfortable because you do not want to be this persons friend. I feel you are right because it also effects you if she is friends with this person. You are more important than this new friend and a choice should be made. You are uncomfortable with her being friends with him, then it should be explained and she should consider your feelings. Anything that is putting a strain on your marriage needs to be resolved. If you are uncomfortable about hearing about him, then she should not talk about him out of repeat for you. Her being friends with him is her being friends with him. You do not have to be friends with him and you do not have to hear about him either. You both need to focus on each other and you went through her cheating before so you both still need to focus on you and her. I would tell her that you both need to focus on each other to build a soild marriage and this friend is an interference in your marriage.