My Dad's cat Miss Kitty (who looks like Squeak's long lost twin) will bite sometimes for no reason. With her I think it's over-stimulation. After my Dad spent a few days at my sister's a couple weeks ago Miss Kitty was very excited to see us when we took Dad home but got a bit too excited and bit Richard on the hand when he was petting her.

The first time she bit me was a few months after she showed up at the house and I pet her too far down her side - I didn't know she didn't like that. Luckily I was wearing a sweater with a shirt under it so the damage wasn't too bad but she bit a hole through both layers of clothing. The next time she bit me really hard was right after my Mom died. I think it was part of her grief.

Anyway, to finally get to my point, maybe Squeak gets over stimulated from the wiping motion. Does she only do it when you are moving your hand/arm? Does she do it when you pet her too much?

Hopefully your vet will have some insight on the matter.