Will you please convince me not to let her in again?

She's been my best friend since we were little kids. I have always had a dysfunctional friendship with her. We are constantly fighting. It usually starts off with us joking and then it turns into a big fight. On Thursday morning I joking there an apple juice cart at her thinking it was empty but there was a little left in it so it spilled on her and I apologized and she retaliated by throwing syrup all over my hair and some on my dress. I mean I didn’t maliciously get her a little wet she really crossed the line. That’s the straw that broke the camel’s back. I’m done ok. I’m sick and tired of fighting I get enough of that at home. I want to mature be my own person and simply be happy and I know my home life is disturbing me but it’s another when my best friend starts hurting me. I’m tired of all this fighting and she didn’t even apologize to me. But even if she did I refuse to forgive her because the cycle will start all over again. I don’t want to be played around with anymore. I have flaws I admit but I’m trying to fix them and this is the first major step I’m taking. Please help convince me not to go back to her because I know I will if I;m not strong enough which I’m not.