does she like me and when should i tell her?

im in tenth grade and i really like this girl who recently broke up with her boyfriend. I think that she may have some feelings for me because she flirts a lot and we talk a lot. The summer is coming up and I really want to go out with her over the summer. Also, her sweet 16 is coming up and i want to do something special for her birthday, any ideas?

the reasons why i think she likes me is that and i posted on twitter who wants to go to the movies later, im so bored. She favorited the tweet even though she had something else to do that night. She seems to talk a lot about me with out me being there such as talking with our teacher and her friend about me. and she always calls me by my full name instead of my nickname and i asked her why shes like i like your full name :). And whenever talking to her on facebook and when i have to leaves, shes like nooo dont go and when i say i have to she says ok bye :). what does this mean?

and when should i tell her, should i do it now or wait 2 weeks until school is over and then ask her to go to the movies or something?