Is it wrong for me to seize contact with my best friend months after she did the same to me?
Does your friend have a reason that she's doing that?
No clue she was so cruel to me.
It's unhealthy for you to treat someone badly in retaliation for how they treated you. If you express how you feel about her actions toward you, it will help you to move forward and maybe re-establish your friendship.
I'm going to turn into a bitch and stab her in the back.
It would be good for your friendship if you let her know how you felt when she stopped talking to you. Seeking retaliation will only ensure that your friendship is not rebuilt.