This one friend really really betrayed me, and a year later she is trying to contact me. I want to not be really friends with her (I know it sounds mean). I dont want to get hurt again though?

It doesn't sound mean to me. It sounds like you need to protect your feelings. I agree with Rooster.

I forgave my brother and sister over and over and over and for 30 years, they always said "Oooops I'm sorry and I'll do better" neither never stopped.  I ended our whatever relationship a year ago. We're all 3 very happy. 

Betrayal can be hard to forgive. It's one thing I have a real problem forgiving. I think it would be best to cut all ties and not respond to this person in any way. I found in all my years that once someone betrays you, they'll do it again. Save yourself some pain and distance yourself.

It doesn't sound mean at all! In fact, I think it shows a great deal of maturity to understand what is truly best for you. There are too many good people out there that would be a better friend to you, then someone who has betrayed you and proven not to be worthy of your friendship. Value yourself and others will too. 😊