Did they get rid of the function where you could choose your own frame out of a choice of three? If so, that's diabolical cause a random thumbnail sometimes sucks.

Uhhh you aren't the center of the universe, and its incredibly selfish to wish someone not receive a diagnosis that may help them understand the self and navigate the world. That's what diagnosis did for me. The thing is your autism isn't the same as my autism nor is it the same as your sister's hypothetical autism. I get wanting to feel unique but you dont even have to set yourself apart with that, you're already unique by being you. Instead, why not value what you can share and teach to your sister by giving your perspective, and then listen to hers? That is much more valuable, and if you keep an open mind to her experience(the key point in any interaction) as unique to her as well, I am sure she will value your support.