I don't like my best friend's boyfriend?

My best friend and I have been friends for at least over 8 years now and I always want the best for her. I mean she's supposedly "in love" with the guy but even I know that it's just puppy love. I feel like she can do so much better. He was a smoker and a drinker and all he would do was just try to get with girls. She met him off Instagram which I think is pretty sketchy idk but at least they get to meet often since he lives nearby her town. Anyways she says supposedly he quit doing all that stuff but who knows. Also I know for a fact that he doesn't come from a good family and goes to an sorta okay college (big factor if they ever want to get married since our parents do sorta of an arranged marriage.) Another factor is that he's 6 years older than her and she's not even legal yet. Last year when she was dating another guy she was telling me about a 22 year old guy who would just hit on her and my friend and I warned her about him (it's the same guy btw) and to stay away because majority of these guys just want to play girls. However she would still keep in touch with him while dating the other guy and ended up breaking up with the other guy because of him. I know some people will say age is just a number but honestly it's still weird in my opinion and my other friend agreed with all the things I said. Sorry it's all over the place but I'm just worried about her once she gets to college and won't be able to see him, what he will do while she is gone? Any advice? Thanks!