What are you trying to achieve?
Not showering? Or having some kind of support?
Instead of focussing on just “I have autism this is hard,” why not look into what might help you, so you can give your mom a clearer idea of how to support you.
For me, showering is so easy not to do at all. I have things built into my schedule which require it, though. Like massage (I feel obligated to be clean for that, and have a routine getting ready for massage). Also I’ve identified things that make me feel gross about being unclean, like when my hair is greasy, and that stays on my mind now once I notice it.
Also if you’re still under 18 (or whatever the age of adulthood is there), a diagnosis is probably a good idea because there may be support available somewhere.
Neurodivergence includes a lot of things other than autism, and I think it would sometimes be hard to tell who is neurodivergent and who isn’t. There are plenty very social people with ADHD, for example.
So it seems a bit silly to have “us vs them” in mind. Because you don’t know. Are you suddenly going to turn tables on someone and agree with them because they decide they’re ADHD?