So, there is a girl in my astronomy class that I have been talking to after class, I walk her back to her car most of the time. She is cool, down to earth, we have the same interests etc.. About a month ago I said we should chill some time she is like definitely so we exchanged numbers. I called her but she never answered, except for some of the text messages i sent her. She said she loses her phone a lot or she is busy. Just this past Wednesday, I'm talking to her and she asked me If I'm got radiohead tickets yet, I'm like nah, she said well my dad can get good deals on tickets, would you like to go with me? Im like hell yea. I ask her if she wants to goto this party friday at a club my friends band is playing etc. She said I can't cuz she is going to be in a play at the same time as the party. I said I would go but I dont wanna miss this party she replied well Its playing thursday, friday and saturday. So i said ok Ill come thursday. I goto the play she was in and after the show I walk over to her and she is talking to some older woman thinking it was her teacher or something. So I say hey, she looks suprised I huged her gave her a kiss "OMG you came i didnt see you in the audience do see the whole thing?" I said yea it was good, she smiled. She introduced the woman she was talking to I didnt hear exactly what she said, I think she said this is zacs mother and I thought to myself ok...who is zac. a group of people come up to us that were in the other plays were on the same night. So their mingling Im standing there not saying much. Then she introduces this guy that was in the play named zac and says nothing else. So I shake his hand. After awhile they are talking to each other, they start kissing and then it hits me ( I felt like ben affleck in chasing amy when he sees the girl start making out with the other girl) She never mentioned she had a boyfriend and was upset, I would never would of persued her the way i did. What should I do/say? Just stop talking to her or ask her why she never mentioned her bf. Should I just try to become good friends with her and when she breaks up with him, sweep in? This isnt the first time this has happens. I always end up liking girls who have boyfriends. Maybe I should ask the girls stright up if they have a BF before I get to involved. But she should of said something when we exchanged numbers right?