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

Update: I realized after, while trying not to say any of my best friends business, I ended up making this post sound much more selfish than it should have. Thank you for all of your opinions I just feel the need to clear things up a bit.

When I said he did some sketchy stuff I mean from what I see it seems like hes manipulating her and preying on the fact that this is her first love and hes older and she doesnt know how guys can be because she used to be lesbian. He makes sure she's wrapped around his finger and it seems like hes trying to isolate her from me. He's done something else that was unsafe sexually but that I will keep private.

So as someone who knows how guys can be and has been in relationships with manipulative people and knows how much a relationship like that can mess with you, im concerned for her. And I feel like I'm losing her and im getting pushed away from her when she might end up needing me. and yes it hurts me because she's my only friend but the part that bothers me most is that shes happy now but I can't see this lasting and it will hurt me to see her hurt from this guy who has her all wrapped up in him to the point where she is a different person.