My friend who I liked for a long time, kissed me while we were both out drinking?

I have liked this girl for two years, she and I go to school together. I have liked her pretty m uch from the start of everything. We developed a very close friendship and told eachother about our respective love lives ( this tends to be our topic of convo). Anyway, once i realized she wasn't over her ex-bf and probably wouldn't be. I went forward with my life and moved onto other people all the while maintaining this very close friendship. I was seeing a girl and things went south and I was talking to my friend about it. We were out with a lot of my friends on my birthday. We went to another bar and pretended to be a couple for fun. Outside the bar she kissed me. Stopped, then I pulled her gently back. Our friend picked us up and we continued kissing in the car. I think i muttered something about this not changing anything. The next morning I saw she called, I called her it was awkward at first but then we laughed. I went out the rest of the weekend and partied and hooked up with other women. I drove her to this thing that week where she proceeded to talk about a fight she had with her ex-bf about 100 times. Her bday is coming up and I am invited. I'd like to kiss her again and see where things go, but I am absolutely petrified and this is very very rare for me to be scared about engaging a woman. Thoughts?