<human>: Condense the text into a few key points

So my sister's friend spends a lot of time here, they've been friends since elementary so i've seen her grow up over the years. Despite that I don't see her as a little sister, and I have always admired her, she's incredibley smart and funny.

Lately we have been texting and b.s.-ing and all that. When she comes over we tease each other, and there are few specific things that make me think there might be something there.

First off I came out of the room from lifting weights and she was here and told my sis that I look good lol. So there is a physical attraction if nothing else. Another occasion she was over and asked me to massage her shoulders, and always asks me for help with her hw even though she really doesn't need it. She will go out of her way to lean her head on my arm, and one time I was peeking my head out the door and she was trying to get in acting all tough and we came really close and I swear we were about 3 seconds away from kissing.

The other day I had a dream I kissed her and when I woke up I started to see everything in a whole new light. She called me and asked me to go to the movies with her. I said I'd thinka bout it to which she said "no, say yes" so I did. So if we do end up going and we are sitting there in the dark faces inches from each other, I don't think I can promise that I wont kiss her. She is very cute. 

Of course the problem is my sister, I wouldn't want to ruin their friendship but to me it seems like her friend pushes for it to happen, unless I am just seeing things.
<bot>: Sisters friends and I have a weird lusting tension that I may act on if we go to the movies. What do I do?