Should i ask this girl out, i'm so nervous?

Okay it's rather complicated. I am in the seventh grade. and there is a girl i really like, and i have tried to be Friends with her innocently , i actually like her personality and go over and talk to her, sometimes i felt like i was bothering her but i know she is naturally kind of reserved.so I was talking to my "Friends" and i let it slip that i like her, and now everyone knows and for the first day or two she didn't even talk to me and it's really awkward. I heard the way she reacted was" i don't know how to respond to that" so it obviously caught her offguard.She smiles at me and sometimes, especially recently, she's stared in my direction, but i don't know if it was at me or just space. I have never dated or asked a girl out, actually i have no experience with girls. Two more important notes She's leaving my school next year, i may also,both in city though, and i am very slightly chubby and portray myself as wacky or goofy even though she is laid back and calm.Also i get super nervous and forget everything i plan to say when i'm around her. SO i may seem annoying or idiotic to her even though i make good grades. school ends in eight days so time is ticking, we are having field trip to the movies soon so maybe something there? Final note I leave the city every summer for half a summer could i still keep some relationship through that? So my question is Does she like me, we talk but i feel that i seem clingy or wierd but it might just be me. Should i ask her out, if so how, when? Can i still keep a friendship on facebook with her either way?, this friendship is important to me. Please answer these qeustions and others in the story. please be sincere i really like this girl and want to still be friends no matter what