Yeah, I mean we could REALLY get into this subject but there's quite a few things at work here. For one I'm *just* young enough that I might have been diagnosed as a child or adolescent, but the whole, "only boys can be autistic" thing was still pretty strong when I was growing up and even with a diagnosis they would have put me in remedial classes rather than addressing the actual issue. I don't know your age, but I imagine it's something similar.
And then on top of all that not a lot of middle school and high school math teachers are truly comfortable teaching math so they'll only teach the approach that worked for them. Then, layered on top of *that* is a hefty dose of misogyny where they won't even be willing to help you if you're floundering because "girls aren't good at math."
But yes, I've found that if I get a teacher in math who is willing to use non-traditional approaches or if I have the materials to just teach it to myself I tend to do just fine. It's not at all a matter of being bad at math; it's just only taught from a very narrow exclusive perspective so a lot of people - I suspect even people not on the spectrum - grow up believing they're bad at it.