I can’t help but wonder why you hate your sister so much when your parents are the problem. They have raised her to behave this way! She’s still a self-centered teen. Eventually, she will ask the same question. But for now, she is getting away with what she can as a way to prove that she is her own person. It’s not attractive, but it is typical.
Why not try to have a talk with your parents? Is there a secret that makes them want to coddle your sister? Have they just run out of steam? Do they need help for parenting a child who is so different from you?
You are old enough to get past petty sibling rivalry and to ask questions instead of making accusations. it sounds to me like they need help, not recriminations. If that’s the case, only you can decide if you are the person most able to provide the help or whether you want to recommend that they talk to a therapist or another helpful resource.
I wish you well.