What is my ex trying to do? is she trying to make me jealous or does she generally like this guy?

Sio ive noticed my ex getting physically close with guys around me. Touching them on the arm orputting her legs over theirs...shell lock arms with them. There is one guy she has shown more interest in. She flirts with him alot. I know in a game of truth or dare she kissed him and when its brought up she gets very defensive saying she was forced since then though theyve been flirting alot. Friends have been talking about them *******. They havent yet. Her best friend who is my roommate said that the boy was flirting with her and she was indifferent and that she was playing along...she's not into him, just bored. Is she trying to make me jealous with this guy...we are all in the saxme group of friends. When at the bar the other night her and this boy were sittin at a table to the left of me and then move to the table aceoss from me. My friend said my ex would occasionally look over at me. Is she trying to make me jealous cause its workin lol whatever just curious