<human>: Can you provide a brief overview of the text?

So we both have the same classes in college and every morning we meet up before class and go together. This morning she didn't show up so I called and text with no reply so I imagined she just overslept like she has before. Later on I see that she read the text I sent, but still didn't reply. So I call her and get sent to voice mail twice and then on the third call she answers. She tells me she didn't oversleep, so I ask her why she didn't make it to class out of curiosity and she gets seemingly annoyed and says that she doesn't need to keep me updated on every little thing she does in her life, and that she was with her mom and went to a doctors appointment. 

I've received this type of answer before at something silly, and I was kind of put off by it. I tell her that I'm not trying to pry into her life and that she doesn't need to tell me her every little move, but that I only expected a simple reply to my text and call telling me that she wasn't going to be at class today. Instead of me waiting for her. 

You see, we kind of have this routine for the past couple months where we go to class together etc, so when something that changes that routine happens such as her going to a doctors appt, is it too much of me to ask for a notification on this? I feel like she's viewing me as some needy boyfriend who needs to know her every action when in reality I'm only asking that she let me know if she's not going to be somewhere when I expect to see her. 

When I tried to explain myself in this, she just wasn't having it and resorted to what she normally does and replied with sarcastic/pissed off answers, when all I am trying to do is have a mature conversation of how I felt. This happens way too often. I'll feel a certain way about something and when I try to explain my feelings or thoughts she makes it seem like I'm just blaming her or telling her she's wrong. How can I talk to her about this? How can I fix this issue?
<bot>: Gf overreacts at smallest things out of nowhere, makes me feel like I'm wrong for expressing my thoughts/feelings when I'm just trying to understand her POV also and grow from these occurrences.