Why is my girlfriend so complicated

Registered since: 12/2011
Incredibly Complicated Girlfriend?

I've been with my girlfriend for just over a year now and I'm incredibly happy with her, (almost) always and in (almost) every situation. Really, I've never been so happy with a woman. It is she too, I know that. Our (long-distance) relationship is really just great, to the point where we argue, it is constantly reproachful and doesn't stop accusing me of things.
As soon as one thing does not go well in our relationship, it pulls our entire (long-distance) relationship into the mud.

I am writing exams shortly before Christmas and therefore have to study EXTREMELY for university, she asked me if she shouldn't come and see me. And I told her that I really have to work a lot and that we could hardly do anything and that I was always in a bad mood and stressed during the learning phase (she knows that and that is how it is) and that I would rather avoid it.

She was okay with it at first and Boom 2 days later she goes completely crazy because I talked to a friend (who happened to walk past me) for 30 seconds while we were on the phone. Ok, that was within 50! minutes cleared.

Today the next argument, again a similar situation and she ticks completely off and then slams me on the head that I would be rude to her and that I would not want her to come and visit me either! Then I don't know what to say, I just want to be supported by her during the learning phase and I let myself be distracted by things so incredibly quickly when I am learning, that's why I always study completely alone (without friends) and just cram completely alone all through. But I have no idea how to tell her that.

If she's hurt like in this situation, then you can't talk to her, she slams all sorts of things on my head: "This long-distance relationship sucks", "Just do your thing and leave me alone", "If you can't get work and girlfriend under one roof, leave me alone ".

The problem is then that she hurts me so much that I can no longer talk to her even though, in her opinion, I did something wrong. If I don't get in touch because she's hurting me a lot after all, she'll accuse me of that too.

The "sad" thing is that everything is always great between us, but as soon as we argue I always think that I can no longer do that, because everything goes according to her nose in the arguments and in the end I only have the goal to calm her down instead of saying what I really think (probably that's where the mistake is)