I admit that a lot of guys are clueless; my husband certainly was. And there are girls that, when they find out a guy is in a relationship, seem suddenly, irresistibly attracted to him. I can't say whether this is one of that sort or not. But I think that most girls are socially savvy enough not to attempt a full-on sexual assault (come on, let's be fair; isn't that what we call an unwelcome attempt at a kiss when a guy does it?) without at least some encouragement. He was enjoying the attention, and encouraging her. When he found out what her intentions were, he should have broken this "friendship" off there; he is still encouraging her. To me, the question in your mind shouldn't be "why is he doing this to me?" but simply, "why is he doing this?"