I really HATE my friend's boyfriend but i promised to be there for her?

Eventually this guy has no respect for her nor her friends (you), he will not last with her for a long time, I can guarantee it. Right now your friend is so into him that she is blindsided. Your best bet is to stop telling her what to do since you will not get nothing out it. Just stay put, she will soon be running back to you since her relationship is nothing serious. My advice: Stay far away but close enough from her.