How to tell if this girl is actually interested or not?

there is this girl that i like and im not sure if shes playing the hard to get game and shes interested or shes just not interested at all. she goes to a different school me being in yr 12 and her in yr 11. i only really see her at 18th's and partys and we talk quite a bit on facebook. i found out a while back from one of her friends that she felt something towards me although i dont no if those feelings are still there. at partys she is always dancing with a friend around me and stares at me a little, i also notice when she is talking with her friends and i walk past she stops and looks at me and so do her friends and sort of start wispering things. although whenever i ask her to talk or dance she seems really shy and seems like she feels a little uncomfortable so i decided not to try and hook in straight away, so last party i asked if she wanted to go outside and have a little chat on our own and so we did and we were havin a good convo and then she just said i needa go back to my friends although she still stuk around for abit, i didnt no if this means ';i dont wanna hook up or have anything'; or if she was just a little nervous and wants me to make the first move, i feel as if the only way i can initiate things is if i hook up with her, cause atm since we go to different schools and only really spk on fbook cha that i usually start, and also partys. theres not much i can do to start things off. how should i approach this????How to tell if this girl is actually interested or not?
Since everyone's so different, you shouldn't try to read too much into a statement like ';I need to go back to my friends';.



For one girl, it might mean ';I need to get away from you b/c I don't want to hook up';

For another girl, it might mean ';I'm super attracted to you and nervous and can't think of anything to say';



If you know one of her close friends well, maybe you can ask them, or better yet, just ask her straight out. I guess it could be awkward if the answer's ';no'; but at least you don't have to be stuck wondering forever and dancing around facebook.



Hope it works out!