Help Please!!! Can you give me some advice on what to do?

I am really starting to like her a lot. Ok so me and my best friend have been friends since 6th grade. We are both 17 he has a sister who is 16. She has always been really sweet to me but I am a really nice guy. Last year I started to like her more and more. Last year when we were working on a project she came into the room and she was wearing a pretty short skirt. I was working on the floor but she kept walking by me even though it wasn't the shortest way. I have this feeling now looking back at it she wanted me to look up her skirt. I never really paid much attention to her though as I was working on the project. We have become closer friends (me and his sister) and a couple weeks ago when we were watching the NFC championship she sat down on the couch next to me. The thing is I had my hand out and she was wearing a skirt and she sat down with her panties on my hand. She then slowly rubbed her on my hand. It may not have been on purpose but what do I know? I think she likes me. I don't know what my friend would think though. Can you please help me out? Do you think she likes me? What should I do? Thanks and sorry I wrote so much.