A fidget spinner is merely a toy. It is not to do with causing autism nor to do with a disease. I was using one today in a big group of people simply because I have social anxiety and used to do other things such as pick at my skin and bite the inside of my cheeks as a way to distract myself. It was nice to actually try balancing it on all fingers rather than scratching my neck. What you consider a trend or a meme is actually useful to some people. There is no need to be so judgmental. It's not your job. Just do what makes you happy and not publicly shame others for what makes them happy.
Let me guess, shes a white blonde, wearing sandals with socks, wears a nice a** pair of glasses and is home in a protestant family.