Am I crazy or is she?

So my little brother (19) just moved out. My mom calls him every day and if he doesn't call her, she freaks out on him and then ends up being mad at everyone. I still live with her (21) and I'm moving out next month with my fiancé. I have a 5 month old. 
She apparently started her period today. Someone knocked on our door and I decided to look out the window first before answering it (which pissed her off). 
It seems like she gets mad over everything? Even when she isn't on her period. I feel like when I move out, she will call me constantly and flip shit if I don't answer or talk to her every day. 
I was cleaning all day until she decided to act like a b word. So I went in my room with my son to get away from her. 
She also went in her room. I have a feeling she's going to start a really bad argument with me. She has hit and pushed me before and lied to everyone saying I pushed her. I'm only 109lbs.. She's over 200lbs.. So there's no possible way for me to push her. She pushed me infront of my son when he was 3months old and it make him SCREAM his head off. I decided to leave to go to my so's house. I was on the phone with him and she was screaming "GO TO THAT DOUCHE BAGS HOUSE HES A PIECE OF SHIT). Really loud so he can hear her. 
I'm not sure if she's mentally ill but every time something like this happens, she never says sorry and always ends up making ME think I'm in the wrong so I apologize every time..