Do i have a mean mom?

I have a sister and my mom always favors her. My dad always treats us fairly though, and he sometimes tells my mom to lay off when she is criticizing me and being rude. I just got my learners so me and my dad went to pick my mom up from work and it's weird because at work she seems like a totally different person and fake and when she gets in the car with me and my dad she starts hurting my feelings and just keeps yelling at things i do wrong when i drive. and she always says i dont help out even though my sister and i do the same amount of work and she was like "I need a big glass of water" and i said so do i" and she was going in the kitchen and i was too to get a cup but she had two in her hand and i though one was for me but it was for my sister and her but my sister didnt even say she wanted water and she went right past me but she could have easily got another cup she just doesnt care about me and she never is on my side she ALWAYS looks out for my sister and finds a way to hurt my feelings.