constantly scratching her eye with her foot usually indicates something is irritating her eye, eye lid or area around the eye. If it only happens in the bath, could be water getting into her eyes and irritating it.
It is always possible she does scratch in her cage but you just don't see it. When giving a bath we tend to watch far more closely than just observing in the cage once in awhile.
Check her eye closely, use a magnifying glass if you have one for any signs of infection, something in the eye, redness or swelling. If you find any of these, take him to a vet so they can determine what is causing it.
If there is nothing you can see and after watching him in the cage more often, and he doesn't scratch at all, I would check water temperature, be careful he doesn't splash water in his eyes or make sure there are no strong chemicals or fumes (including scents from soap, bath oils, etc that may have been in the sink before you give the bath).
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PHLdyPayne