Why won’t my sister just accept the word NO?

My sister is autistic but she is dead smart, will greet you hello and shit like that, BUT she is such a pain in the ass. I know that her brain works differently than us but that does not mean that she can’t learn boundaries or whatever. But when things don’t go her way, she thought a huge pepper tantrum in the problem with my parents. Keep enabling her just because she’s “special needs”. What so special about her? Some of my relatives say she’s special but I don’t think she’s special at all. She’s just like everybody else she gets has really huge ego because people are telling her that she’s special. Or when she gets a question wrong, and if someone gets the right answer that she gets really upset as well. When she asked me where I was and I told her I was at my boyfriend’s she asked me what did we do and I told her we just hung out with her she said what did we do and I said it was none of her business and I’m not telling her. She repeatedly asked me where like six times and then I snapped at her and told her to mind her own business and fuck off. She looked at me and told my mom that I was being mean to her and then my mom school that me and reminded me that she is special. I need to take it easy on her and I’m like no. Even my aunt and uncle has told my parents that their baby, my sister too much and she needs to except or have hard talks about life. I blame my parents were enabling her all her life and spoiling her. She hates being told no and this girls like 16 years old she should know better she’s going to be in for a rude awakening.

Updates
11 mo
My two brothers and I are fed up and we don’t even spend time with her much because she’s exhausting.
Why won’t my sister just accept the word NO?
Post Opinion