Advice please ladies.?

my girlfriend openly admits that shes crazy/irrational/ and a 'hard pill to swallow'. 90% of the time it has to be about her. She hates her job but wont find another one, shes a great person who everyone likes and people even strangers are open with her and she is a magnetic person. But she is so hateful. She resents anyone talking to her or sharing their opinions or offering advice. Instead of dealing with it directly she just smiles and plays along and then when shes around me all she does is emotionally breakdown and rage about how sick and tired she is and how the worlds unfair (to her) and people need to leave her alone etc. This is nothing compared to how she reacts to her mother. LONG STORY SHORT.. her mom is a kept woman who divorced and remarried only because of money. my girlfriend has such internal problems with her mother she cant stand to be around her, and now that her mother and stepfather are helping her finacially in order for her to return to school. My girlfriend has meet with them occasionally to discuss finances and etc. WHERE I NEED ADVICE: like clockwork when she even thinks about her mom she gets anxious and angry and anything she says is a potent attack that destroys my girlfriend and she can barely speak. But ive been with her at her parents and the reality is her moms just like any other mom, she has an opinion. I feel bad that i cant keep the delusions my girlfriend has about the injustice she suffers. I try to understand and cant. i tell her its all okay and try to help soothe her (what she asks me to do) and then she erupts that i dont know what im talking about and how bad things keep happening to her and how i dont understand etc. Is it so bad that i feel shes being unfair, that shes selfish and ungrateful. she complains she doesnt have something,, then she gets it and she complains that she had to work for it or earn it or if it was given to her that she has to be thankful for it. Why cant i stop feeling like shes an immature brat and get upset because im supposed to be there for her whenever shes upset. SHE NEVER COMPLAINS TO THE PEOPLE SHE NEEDS TOO. i have to hear it all, she projects everything onto me and if i even show an ounce of (ohmygawd here we go again) she freaks out and acts like im somekind of abusive tyrannical jerk who never cared about her and how she can treats me so good by not belittling me or 'being mean' and then we go through the dance of me putting for all this energy to soothe her and promise that i'll put her feelings and thougghts and well being far above my own and how i will rake myself over hotcoals in the hopes she might have a moment of unsuffering joy. i only know whats in my head and heart. i want people to please give me a glimpse into the inner workings of the emotional wreckage in a selfish girls mind. I need real advice to help me understand and find the compion i need. please