Is it understandable to break up with my girlfriend, because of her family life?

My girlfriend's family life is SOOOO screwed up and corrupt, its REALLY messing with our relationship. She's always in a bad mood, we can NEVER see each other, she's also completely untrustworthy due to her stories about her past and that she has another boyfriend that she had before me, but refuses to talk about him, add me on facebook, etc. I know its not serious between them, because all of her friends and family only know about me. Would it be understandable to break up with her, because I dont know if I can take it anymore. :/