You sound more jealous than selfish, to be honest. I mean, you stated that you loved May/December relationships. If I was your friend and knew that, I would assume that you wouldn't mind being in one. I would also assume that you would be one of the few people who wouldn't judge the relationship and get it. I would expect you to be supportive. Which may be why she talks to you about it so much. And for you to say you think he's using her (whether he is or not) would ring in her ears that you're maybe jealous. I don't know what your situation is (if you're in a relationship or not), I'm only going off what you've said. I'm probably wrong, but it's not a bad idea to look at things from your friend's perspective.