relationship question...HELP

Me and my ex-GF started dating when I was 16 and she was 15. Their were no problems between us, maybe a few discussions but nothing serious. We were perfect. When i completed 18 i went to study abroad (Madrid), and we had a distance relationship (2.5 years). The relationship totally lasted 4 years. The problem started when one of the christmas holidays i came back, i started to smoke a lot of weed, which she really hated. I had a lot of problems and i was really stressed (because of the studies), that´s why i started smoking. I know its not an excuse. Then i started to study in a new city (London) as an exchange student and as i was new in London, I had a problem adjusting to the city. During that period I didn´t call her for 3 weeks. I know its my fault and she left me (March), although she kept giving me hope that we would return. I was devastated and lost a lot of weight. When summer arrived i went back to my town and she said that she had changed and she didn´t see me in that way anymore. She also seemed different. I know that can happen, but in a few weeks she made out with one of my best friends. I coudnt believe it and i spent the summer doing an internship hoping that my classes would start. Obviously we stopped talking. My friends in a way also spoke to her less (they were also her friends). When I arrived to Madrid, she sent me a message, telling me that she wanted to speak to me. My friends told me that she had told them indirectly that she felt sort of bad about what she had done. The other other "best" friend of mine who made out with her, has not called me yet. But i don´t care about him. I never answered her. It was the best decission. That year was fantastic and i got over her (thats what i think). After the summer, Someone we both know was getting married. It was kind of a surprise/shock because i didnt expect to see her in the wedding. A bit more than a year had passed since i last saw her. But i just said her hi and acted normally. But I felt bad because many of my friends when we were dancing didnt talk to her much. Then she suddenly grabbed my hand and told me that she wanted to speak to me. She asked me a silly question, it was like an excuse just to talk to me. I feel really bad because i kind of ignored her and told her someone was calling me on my cellphone, and just left her their. I dont know why but this time when i looked at her she reminded me of the girl who she used to be. Then my cousins told me that when they spoke to her, she was really polite and she asked for me. Obviously they told her I was doing fine. I dont know why but do you think that maybe i should have spoken to her? are there still feelings (or are they resurfacing) because she was my first love? please comment