Ok heres a brief summary about my problem:

My sister has a friend that I really like and she likes me but she seems to like my bro also. The thing that makes me mad about her is that she shows affection towards me and then forgets about me and shows affection towards him. Ex: I walked in on her in the bathroom while she was getting changed(I didnt see too much) and she just looked at me like nothing was wrong and I said sorry and closed the door and then she asked me how she should do her. Then she starts talking to me in the living room and then she goes and sits on my bro because he wouldnt change the channel on the tv. That really pissed me off and I just left the house to hang out with my friends so I can cool off some how. She has a boyfriend too and Id rather see her with him because my bro says bad compliments about her and bothers her and stuff(which I dont and I tend to give her good compliments from time to time)

What should I do? Should I get over her or give her one last chance?

Shes an attention whore. Back away slowly, then run like your head is on fire and your ass is catching

Yea I was thinking that but I would like to be a close friend at least.

She sounds like a definite whore, but you could probably get sex out of her if nothing else.

She's just flirting with you, she really doesn't give a shit about you. Drop it.

Not worth the trouble dude.

Attention whore all the way.

^ What they said.
I hate girls.

This gave me teh lulz.

That me lol too