Help!!! stoopid girls!!?

last weekend a girl told me she liked me. we went out to eat with my roommate, watched a movie, ended up making out. Last night she asked me and the people i was with if we wanted to go bowling. We went to her room to meet up with her and she was with another guy. They rode together, got there he was flirty, you can tell he likes her, I totally ignored her, and played really aloof. I asked my friends what they thought of it and they said he wants her but she is using him as an "Ornament" to get me jealous, and they thought they were just friends. we havent talked since last night (and we didnt really talk much last night). What is your take on this? we are freshmen in college btw both 18