She will start counting things. Everything. Physically, as one finger up going from piece to piece as she counts. It's not constant, but often enough - things like standing in front of a person with freckles and having her finger up in the air to count how many freckles there are, things like that.

She won't be able to stop this herself once it has started, but if someone/something interrupts her (like drags her away or whatever she is counting leaves) she won't feel the urge to continue or get lasting damage from it. But she can now be stopped by a building with many windows or, yes, by someone emptying out a bag of uncooked rice in front of her.

If this does not work and you'd rather have something else, please say so.