My brother has a girlfriend, and she is insecure has anxiety problems and just in general is a strange person ( I'm not judgemental) it's just the vibes I get off her.... in her insta at least twice a week she posts something about my brother being gay and does so on snap chat a lot as well, last night I finally blew and phoned him and told him how I thought it was pretty nasty and horrible of her as his gf to do this, not that I'd be bothered if he came out gay, but its the simple fact that he is with her and she does this (she is sexually insecure and doesn't know whether she wants to be a male or female). My SO and i tried to get him to see that this along with everything else she does/says is abuse both mental and emotional, but he doesn't see it, my parents are concerned about him as well. 

Is there anything we can do to make him see what this girl is doing to him? Bearing in mind he is 19 and she is 16. Im at my wits end with it all and ready to send her packing for my brother, and so are my parents, she doesn't eat much at all, and think it's rubbing off on my brother. 

Any advice welcome 

Considering I myself have been in an abusive relationship both emotional and mental i know the signs.