Her intentions might be good, but her methodology sucks (and, if you want my opinion, her threshold for embarrassment is way too low).
In my personal opinion, stims that are quiet, non-violent, and non-destructive should be tolerated in public (and by the general public-- I mean, come ON, normal people do plenty of things that are irritating to us and we're supposed to suck it up and cope; guess what guys, that's a two-way street).
In real life, though, right now it doesn't work that way, and stimming in public (and "in public" is pretty much anywhere that isn't "alone in your room") can get you hurt.
So, yes, you do need to find "normal-looking," unobtrusive stims just to be able to get by in the world. Sad but true.
Your mom's behavior is still messed-up and bitchy, though. Please try not to take her childish, selfish attitude to heart.
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"Alas, our dried voices when we whisper together are quiet and meaningless, as wind in dry grass, or rats' feet over broken glass in our dry cellar." --TS Eliot, "The Hollow Men"