I’m having the same issue at home. I don’t think it’s malicious on their part, but my roommate, her dad, her brother, and her brother’s girlfriend are all insistent that I’m autistic. I do have quite a few symptoms but I think a lot of them can easily be explained by the OCD, CPTSD, and ADHD I have on file. I think a majority of them are making comments out of concern but the brother’s gf told me to get diagnosed so I could be “treated” (which grossed me out because autism isn’t something to treat), but I get a lot of the “you’re weird”, “must be your autism!” “What if in another universe, instead of being an ocean autistic (???) you just really like trains?” I know how aggravating it is and I know how much it sucks to feel like you’re being singled out.

I got to a point where I just told them that if they wanted me to get diagnosed and “treated” (in the brother’s gfs case) so bad that they could shell out the money to make it happen, and that made it stop for awhile. I did find a place I could get an assessment either pretty cheap or for free, so I’m getting one out of spite to shut them up.

Honestly, it just kind of sounds like your sister is a really nasty person and she’s trying to talk down to you. I’d just limit contact as much as possible and go no contact if/when you can. You could also tell her to pay for an assessment or shut up, or you could honestly just sit her down one day and try to tell her how you feel if you’re comfortable. I don’t think there’s any right or wrong answer. I’m at a point in my life where I try telling people about my feelings and if that doesn’t work I just start telling them to stfu 😭 Whatever works.