I met the sweetest girl last night, we liked each other but I left without asking for her number? Facebook her?

[Mike]

So I went to a party at my friend's house and I met this girl there and she was really sweet, we spent the whole night talking and then I was supposed to be going to another party later but she told me to go with her to this other party. I went, it was a gay party, i didn't know and i didn't care she got caught up talking to her friends and I felt a a little uncomfortable so I took off. We didn't exchange numbers, but she's friends with some of my friends on Facebook. Should I add her? Should I wait til I see her again? I really liked her, she was different from your typical preppy college girl which makes up about 90% of the girls at my college. Give me some advice if you could plz.