NTA

Your sister is jealous of you. I think your parents should find a way to discipline your sister. I am guessing your sister has a sense of right from wrong... based on her knowing when she is being treated unfairly. It sounds like your sister needs those feeling cards and one of those talking apps to help with communication. Does your sister know some sign language? I know that people who are non-verbal autistic can learn sign language.

Has your sister ever seen someone for Cognitive Behavioral Therapy? If not, it sounds like she would benefit from seeing someone for her spitefulness.

https://www.nichd.nih.gov/health/topics/autism/conditioninfo/treatments/cognitive-behavior