Mother not being pleased with the girl one wishes to marry

My mum is refusing to marry me to a woman because she didn't find her pretty and she didn't like the girl's family. She says that they are dangerous and that the girl is not good (not respectful). But I know from mutual friends that the girl is righteous and she does her best to follow Islam, even if she doesn't wear Hijab. My mother had heard from a lot of families here that the girl's family is quite special and she doesn't like that. So she is arguing with me to not marry this girl. What should I do? I know from personal sources that the girl's family won't give her hand to me if I don't come with my whole family. Please tell me what should I do?