I still have feelings for her but she only sees me as a friend now, what should I do?

How old are you? I wouldn't have anything to do with either of them, brother or NOT!

Explain why you even need to be friends with a female that goes behind your back with your brother, no less! I just don't understand!

Don't wait around for her. She is not a good person by doing that to you. You need a girl who is loyal to you and loves you.

The answer is to move on and put her behind you.