Counselors and Therapist please help??!!?

My younger sister is a straight A's student.. My other sisters and I are average students.. I think this plays a huge role why my parents favor her more.. She does not show my parents any respect what so ever.. She constantly argues with my mom if she doesn't get her way.. and my mom doesn't do anything about it.. If it was me or my other sisters we would defiantly get grounded.. but with my younger sister, grounding don't even exist, she gets everything she wants.. My mom buys her expensive makeup, new bed, new desk.. and then she gives me all of my younger sister's furniture..For her birthday my mom bought her everything she wanted... for my birthday I got nothing.. why is my parents doing this?

When my younger sister first got her first job. My mom congratulated her with gifts and balloons.. When I got my first job, I didn't get anything..AND I actually waited and waited hoping to get something.. My younger sister got her first car before I did..My family and I went car shopping for my younger sister's first car.. I was happy for my sister, but behind my happy smile my heart is in deep pain..I tried so hard to hold back my tears, you don't even know how sad I felted.. I know my parents loves me dearly but I'm really sad that my parents favor my younger sister more then I .. I'm the only one who cooks and clean.. I'm the only one who basically help out around the house.. I'm the only one who respect my parents I don't ever yell at them like my other sisters.. My younger sister, basically lives in her room.. She don't ever come out or bother to help out around the house.. She constantly talk back to my parents.. She has a bad attitude and do not respect me or any of my older sisters.. She don't even respect my parents, but my parents seems to be doing EVERYTHING for her...

I feel alone. trap inside my own home.. So I started sneaking out hanging out with friends. when I hang out with my friends I feel free and happy.. I try so to talk to my parents so many times, all they do is yell at me for me to stop being jealous of my younger sister.. Am I jealous? I'm not jealous I'm happy for her and I love her dearly I'm sad that they can't be fair, I feel like I'm the black sheep... they just don't understand and they don't even try to understand... My dad recently bought my sister an Iphone.. he just one day went out and bought her one came home and surprise her in front of me.. I was happy for her.. right when I got into my room I burst into tears, didn't understand why my dad didn't buy me one too.. after that all I wanted to do was to escape and go out.. I'm too much pain that I don't even want to stay inside my so call HOME.. I'm trying hard to keep my emotions to myself but I'm at the point where I can no longer hold it in anymore.. Even if I try to talk to my parents it's not like they'll understand.. I don't know what else to do..