I'm SO sick of acting mature

(vent-rant thing idk)

I feel like EVERY TIME I get in an argument with this specific friend, I just have to bottle up everything she says to me so I can be the "mature one" in the situation. If I try to defend myself, I'm scolded for making the situation worse for no reason. I'm literally SO tired of dealing with that asshole. I keep on randomly being texted by her either so she can tell me her negative opinions on me or so I can prevent her from attempting suicide.

I've known her ever since I was a child, and I don't know how much longer I even wanna be around her. She doesen't even understand boundaries at all! She touches me innapropriately and hits me until I'm on the verge of tears and then she calls me sensitive for reacting like that. I still remember being scolded in early elementary school for not being mature and putting up with her bs. She STOLE MY SHOES once and our teacher got mad at ME for interupting her on accident. I don't want to act like an adult and handle every disagreement by walking away or whatever; I want to yell back and actually say what I'm thinking. But I'm sure she'd just beat me if I tried anyway