Help with my mom! please! :'(?

Okay so whenever my mom gets headaches she becomes super bitchy! She gets mad for anything! And I didn't go to school today becase I had a dr.appointment and it was over after school ended. My mom was happy for the day but like 10 min ago she told me to give the attendence office my excuse for not going to school because according to her my homeroom teacher doesn't do anything. And then I tell her that he will turn it in and she starts screaming :"he doesn't do anything that's why you have unexcused abcenses! You know what don't do as I say,get an unexcused abcense,miss prom whatever!" And then I told her:"I don't plan on going to prom and he does excuse me,it was my teacher from last year who wouldn't." Then she goes:" you know what?! Do what you want!" So as I'm walking upstairs I can hear her saying to herself: "freakin life..." she seems to only be happy when she's talking to her family in colombia. She could be mad cause my aunt had surgery and she wasn't there to help her or cause my brother got a ticketfor no apparent reaso. Okay I know its all of this but I feel bad how she over reacts...for everything!