Does this girl like me?

i was in a bedroom last night after a party with a couple girls and this girl i like was laying next to me, once it got abit later and everyone else wennt to sleep, we started holding hands and then she started rubbing my hand over her body in a sexual way and then we started to kiss, we did that for about 3 hours. ive know this girl for quite a wile shes my mates younger sister. I just want to knnow if she actually likes me, weve sort of had flings before and shes said she thinks im good looking. i want her to be my girlfriend, ive always liked her. but really need to know if she likes me or might just be using me when she can. shes two years younger then me im 18 shes just turnt 16 ? help pls