(going to go ahead and apologize in advance for grammatical errors, English isn't my first language)

Hello, the title probably sounds bad alreadyso allow me to give some background info. I work at a very popular, green coffee shop. I don't work super often because I am in school right now (by that I mean I work 15-20hrs a week usually). My store manager is super chill, very understanding. However, our store is a tad understaffed, meaning my manager will often try to contact me to see if I can come in on my days off. I have a lot of days off so you'd think that would be no problem for me, right?
Well, not necessarily. As I've already stated, I am in school. I have a very heavy course load, but that's not my main issue. 

I have a lot of mental health and family issues. To put things bluntly, I had a SEVERE breakdown earlier this month and I am still recovering, emotionally. I was put in counseling (not hospitalized), and have those sessions once a week. I am still having a very hard time and its been very difficult to even go to my scheduled shifts (I still do). For reference, I've only ever called out once. Anyway, the point is that it's been extremely difficult for me to come on my days off. 

My manager doesn't like that I can't come in on my days off to cover shifts. I don't necessarily blame her, because every time she has asked this month, I have declined. However, I can't help but feel angry because she doesn't understand what's going on in my life. I've tried to explain to her that I'm going through a really hard time and it's difficult for me just to even get away from my family for a couple of hours. She doesn't seem to care, saying that I'm not committed enough, and that she needs more from me. I'm extremely conflicted because sometimes I think "no screw her I have a lot going on." But sometimes I really do feel like she's right. I understand why she's upset with me, sometimes I feel like I'm not doing enough for my store, and sometimes I feel like I need to push myself to go to more shifts. Am I the asshole here?

