Hi, I'd like to help you with your question.
Your analogy gives a very good picture of your girlfriend's issue. Having an anger management issue makes a relationship very difficult. The other person always has the feeling of having to walk on eggshells around the relationship and cannot ever truly relax. It also makes it hard to trust because the partner is always on the defensive against the anger and hurt.
There could be two reasons you girlfriend is like this. One, this is part of her personality. Some people are more inclined genetically to be angry, crabby and irritable. That does not mean they are not responsible for their behavior. They need to learn better ways to cope with their personality traits, just like anyone else who has a negative side to themselves.
Two, your girlfriend has a low tolerance for frustration. She feels it is unfair that she has to put up with the frustrations she deals with and as a result, she takes it out on others.
Do you feel your girlfriend is willing to work on her problem with anger? If so, then there are many things she can do to help herself learn how to express her anger better.
1. Your girlfriend can work on her thought processes, also known as cognitive restructuring. When a frustrating thought comes into her head, she needs to realize how she usually processes it then change it. For example, instead of thinking a task is impossible and why did she get stuck with it, she needs to say it's no different than what others are having to do and she has done this before. No big deal.
2. Learn relaxation techniques so she can turn to them whenever she feels the frustration coming on.
3. Communicate her feelings better. Instead of just blurting out frustration and anger, she needs to learn how to express herself in a more acceptable way.
4. Have outlets. When she feels upset, go somewhere to cool down. When you see each other, she needs to start learning to back off and go by herself until she calms down when she feels angry.
Therapy is a valuable tool to help her learn how to do all of these things. To find a therapist, she can talk to her doctor for a referral or try searching on line at http://therapists.psychologytoday.com/rms/.
If your girlfriend will not help herself, you need to decide how you want to react. Outbursts directed at you without insight into how they are affecting you is no way for her to handle her anger and it can be considered a form of emotional abuse. Your girlfriend needs to realize how her issues are affecting your relationship. If not, you may not have a choice but to put up with it or leave her. But before you decide, seek counseling yourself so you know you are making the best decision you can.
I hope this has helped you,