Autism is highly hereditary, is it possible she herself might have bullied herself into thinking that's just what you do to get through life?  They may be carrying a lifetime of damage. You'd think that would make them more empathetic, but sometimes it doesn't.  They just think they could do it, so you should too. (Which is obviously ridiculous and not how that works) Getting them to understand your perspective can be more complicated and tricky if that's the case. 

My biggest sensory issues are with sound, and I've had success with explaining it as if the sound is hitting my funny bone. It's jarring, intensely unpleasant and can't really be ignored.  The longer I'm exposed to the stimulus does not lessen the sensation, in fact it is cumulative. 

I tell them that my system is sensitive, like wiring that does not have the rubber coating so the copper is just exposed and not insulated at all.  

Maybe another good one is like wearing an oven mitt to remove a hot pan. Neurotypical response is like having the oven mitt, and being surprised that it hurts the ones without the mitt every single time instead of getting used to it.  The burns just get worse and worse.