How do i stop feeling this way?

Some days ago, i heard a girl talking shit about me, and today she went out of her way to greet me and strike up a conversation. This made me feel disgusted somehow. I felt disgusted because i know she was only talking to me because she knew that i had heard her badmouthing me, and she wanted to make a good impression, but i don't know, i just can't stand the fact that i'm not good enough to be treated fairly, and that the only way for me to be treated with respect is when they know that i know they're a bitch. I've been feeling degraded ever since