Girl help, all opinion's needed?

Ok, i'm sorry for this but i don't know what to do. This girl i met her before and she used to go out with a guy i know i kinda got to know her this way. they broke up months ago because her and i are in our final year and have exams and he is not in this year yet. her and i both do art and i helped her quite a lot with her portfolio for art college and we became really good friends. Since i'm irish Paddy's day is huge over here and we got together for shots and went dancing and i wanted to kiss her but her friend took her because they had to go home. then two days after on Saturday before we had to go back to school. we met up and had some shots and we kissed in the smoking room and kinda kicked it off, i was so happy. over the next few day's i kinda realized that i was in love with this girl because we both love art, and music and pretty much everything. then i suppose i got kind off clingy because i was calling and talking to her all the time over the next 2 weeks. we're finally off this weekend because our Language examinations are over. I meet her out last night with her friends and was like "would you like to get a drink" and she wasnt drinking, so i was like would you like to hang out for a while but she never replied and went off with her friends and i felt like ****. tonight i went to the bus stop to pick up my older brother and i met her on our way up and she looked beautiful and my brother's jaw was pracitcally on the floor and we were smoking and talking and i said i'd see her later. went out tonight and i never met her at all and i feel so ****. is it me bring too clingy or something like, this girl is really everything to me i never mentioned that i've known her actually for about 3 years. next weekend is my birthday bash im throwing and were having a few drinks with my friends before we go out but she's coming up earlier and on the flat part off my roof i have 2 chairs a table a candle and a bottle of good ole chartreuse and my plan was to ask her then because where we are sitting looks down over the city so i thought it would be really romantic. Thanks for taking time to read this and all comments are appreciated.