Does this girl like me? Should i add her on facebook and talk to her on facebook?

i am 15, i go to this one acting cl once a month and today i saw this really pretty girl, who is 16, we made slight eye contact like 3 times, and she kept looking in my direction. But she was talking and laughing with this 24 year old guy. but halfway through she sat by me. and when would get up and act she moved my chair closer to hers. then when i sat down she would criss crooss her legs infront of me, like 2 cm away from my legs. and then when i got up she would put her legs on my chair. however she never talked to me, nor did i talk to her. Does she like me? and should i add her on facebook and chat with her there?