it really fkn hurts when my mom defends the shit out of my older sister. she acts like she doesn't…

it really fkn hurts when my mom defends the shit out of my older sister. she acts like she doesn't have 3 other kids. My sister is the type of person that loves to run her mouth and speaks without thinking. My mom really just got mad at me for telling her my sister is so rude for trying to put my nephew down. Who tells their 12 year old nephew that is excited to start football that he is no one near football material, and that her husband's nephew plays football and he's all fit with a 6 pack and all at 13 years old. its like stfu and be happy for your nephew, say something positive for once. poor him is all sad saying he doesn't ever want to go back to her house and that he doesn't understand why she puts him down. but my mom thinks she did nothing wrong.and that we're just over exaggerating and we're just running our mouths for no reason. why can't she treat us all the same, she only defends her like that, no one else. it really hurts me :(