Am I overreacting??? please help

Me and this girl were best friends from about 5 years old but around 10 we lost touch. Ever since we lost touch I wanted nothing more than to just see her again. I'm 17 she's 18 now we got back in touch when I was 14. She has the mind of a 12 year old thou doctors have even showed that with test. But everyone thinks I'm much older than I really am cause I'm mature. I want to support her and continue to be her friend but her behavior has me worried. I'll go to visit her and when I go home she will throw a fit n wine n get really angry with me. I even spent 5 days n nights with her strait and still she wined n got really angry with me. She's constantly asking me every time we talk if I'm coming over but I don't want to if she acts like that when I have to leave. I recently told her that I'm moving away in with my bf and I'm getting married in a few months. She wasn't happy for me. She was mad at me and didn't even want to talk to me when I was over her house. She wants me to live with her but that's not an option. I lived with her for a couple days because I had no where to go I thanked her and her gmom for helping while I needed it. She got pissed made a comment about my family (which pissed me off) she wouldn't even help me put my things in my dads car and she slammed the door. We didn't talk for about a week until I called her. She hates the man I'm going to marry for no reason literally she cursed him out for an hour and wouldn't stop no matter what I said and she said she was joking. We both have little brothers hers is 6 and she will curse him out yell at him so Everytime I'm over there I'm stepping because he's just a child. I tried to talk to her like an adult about treating her lil bro better but that didn't help. I already have depression anxiety and many other issues I'm trying to better myself and keep positivity in my life. basically we've both had fucked up past but idk if me and her should remain friends. Is this even a healthy friendship? Am I over reacting?