What is my girlfriend doing?

My gf started a math class in college. She came home one night talking about a really cool guy she met and how she insists he looks like Michael Jordan from the NBA. From then on she would bring him up, saying "I call him by Michael Jordan I dont even know his real name hahaha!" Then he occassionally came over to our house and is there when I get home from work before their class to prepare, usually a gay guy from class also comes and my son is usually playing in the living room during this time. This trio ends up becoming a study group, and they will sometimes give each other rides to and from school. Then one night we got in a fight cuz a girl left a flirty comment on my myspace. She flipped and used this guy against me like something was going on. I freaked out bc it seemed so revealing about their relationship. Since , he doesn't come around anymore and just the other night she gave him another ride home. Turns they are in the same major and are planning to take more classes togeth

sounds hard to tell. she's trying to make your jealous when she used him against you.
its really inmature. you should mention to her that you dont feel comfortable with her spending time with him, explain your reasons...

Quite a lengthy narration and looks like a story. Try to be brief and to the point in your questions.

She's playing mind games.... Dump her and move on!