Grrr to your sister. I hate the "oh, I once knew / was a special needs assistant" trope. Even if they did, it's still not their place to comment. Nobody knows what it's like to be you, and surely folk realise that we keep a lot of stuff hidden / private. Oh, but then of course we get the "But everyone is a bit like that" if we ever try to open up about our struggles. My mother is fully on board now, both with myself and my daughters diagnosis, but in the beginning it was "but everyone is a bit shy sometimes" By the time she had saud that for about the 20th time about a dufferent trait, she realised its about the cumulative total of things. I can excuse her a bit as it's possibly a bit of guilt from not noticing and denial (I've never made her feel bad about it btw)
I hate the fact that we don't fit into people's ideas of what we are supposed to be, what they have read about, or their stupid, ignorant, limited experience. Guess what, ND people aren't homogeneous and all have different symptom profiles.
Yes, I have arguments and conversations in my head most days with other people. I guess it's mostly to say the things we often can't say out loud. And to practice saying the things we really want to say in advance/ next time. Doesn't always work, but I'm much kinder to myself these days about it all.
Oh, and my ex said to me that his mate was an special needs assistant. Imagine his surprise, when his mate actually found out he was "40% Autistic himself" I don't know if this was misheard bullshit, but either way I was sick of the misconceptions and gross deliberate misunderstanding, so I blocked him.