Why did my friend tell my secrets to this guy?

I just found out that this guy and his friends in a fraternity has been asking about me. I ignored him and never went out to his parties. Although, he became really close to my friend on campus. She kept asking me things and i never payed it no mind. Then all of a sudden I asked her and she has been avoiding me. Then where i saw her again she said, " now you know what it is like to be ignored." I was confused because she was always talking about how they were sluts. He keeps staring at me and his friends keep inviting me out to stuff.