What is right...coz i dont know anymore...?

Don't tell her. She probably wouldn't believe you, and think that you made it all up. She would probably think you're jealous of them, too. I would stay out of it, and when she tells you he broke up with her, just hug her and ask her to hang out. But whatever you do, don't lead her boyfriend into thinking you like him, then date him. That would be the worst thing you could do.