Its not worth hurting your friend. Trust me I know.
I like a guy. He's a close friend who's dating a close friend. They fight a lot and may break up soon. The girl is already angry at me as we flirt a lot and I don't want to ruin our friendship any more. I really like the guy and don't know what to do?
First of all, do not worry! You need to know if they will break up or not! If this happens spend a week, and starting then starts talking more with your friend more and more.
If you have luck you're gonna see who can get together :) but be careful! You must be sure that your friend no longer likes your "friend"
You Do know what to do because you know your own integrity and you know right from wrong. You will go with your integrity. Its a choice we make based on our values.