Help- A good friend of my is being used by another friend (they are dating)?

Ok my friend and neighbor (who I have a crush on) is going out with another friend of mine. I was the one who told her they would make a good couple. Well her boyfriend broke up with her and 4 or 5 day latter she started going out with my guy friend.This girl's best friend and her cousin both told me she is just using my friend to get back together with her ex by making him jelouse.

My guy friend is still hanging out with me a lot and even has me ride mini-bikes with him (both of us on one bike) and the last time I went he told girlfriend (my other friend) and she called and was screaming at me about trying to break them up and steal him. When I told my guy friend this he just laughed and wanted me to go on another ride with him.
**~My guy friend and his girlfriend don't see each other a lot maby once or twice a month.
How do I tell him what she is doing?

BTW my guy friend is SUPER sentive

you need to take a step back from the situation. you say you have a crush on this boy, so maybe your convincing yourself, that his girlfriend is using him. if your sure, that she is using him, then it's best if you proof from his girlfriends cousin before you confront the boy.

wow this is like a college algebra equasion. i cant read it. there are too many random usless pieces of information.
but yeah, tell him