Why is she Avoiding me?

So Il begin here. I recently started taking classes at this place in the city. I have the classes once a week and I have been going for about 3 weeks in total. At the first class I was early and I was in the waiting room, this girl walked in and she was always smiling at me and we had small talk and got on. The second week we couldnt talk at the start of class as she was late. After class while we were leaving the building I said that we should get coffee , she said sure and we started walking to get coffee. She was giving me all the right signs, giving me direct eye contact asking me about my family and she told me about hers, she was laughing at my horrible jokes, so all went well and I walked her halfway back home just for the sake to talk to her a little longer, I kept my cool the entire time, words where flowing out of my mouth and talked about education too. Note: shes really intelligent and doesnt have time for going out, ect. She needs to get the highest points to get into med school. So we said goodbye and smiled at each other. Next week class was canceled so the week after she came into class. She did not look at me, NOT EVEN ONCE! It was like she was deliberatly avoiding me, like she never knew me. Now I wouldnt be complaining if we didnt get along during coffee. Some of you might think that only I was interested at the time but Im not that naive, I noticed her pupils going larger and that she was actually attracted to me. So after class I stalled to talk to her while we were leaving, more small talk came with that and when we left the building I asked her if she was free next thursday or friday, she said she wasnt sure(like yes and no) and asked me if I had facebook. She took out her phone and wrote my name in the notes and told me she would add me on facebook, ps. Im not in love with this girl and while we were out gor coffee I wasnt deluded with crap that she was really into me. I clearly saw the signs and felt her attraction(and not only my attraction to her), it would be nice to have a fresh perspective on things,; she is the type of girl who doesnt date and go out that much , focuses more on studying and exams are in 3 months and she needs to get into med school, she doeant have that much friends but I assume she is friendly.