I'm sorry to hear about his family member passing. I would wait a little before bringing up the subject again, but definitely still talk about it...especially if you went away feeling like the bad guy. I'm sure he understood your point, but you might want to clear the air with him. You're not saying he can't talk to her ever again, right? You just didn't like the fact that he was conversing with her behind your back through FB and inviting her to things. Those are valid worries so just make it clear that those are the kinds of behaviors you don't appreciate. I mean, if she seems like a nice girl and interested in the same stuff you guys are, there's no reason why she can't be friends with the both of you, right? You guys should be able to hang out and game together and get to know each other a little more, and then maybe you'll get a better feel for the kind of person she is.