This is not legal advice as I am not a lawyer, but I worked with geriatric psych patients for many years and what your significant other is experiencing is sadly one of the realities of dementia care.

If she cannot handle it and her employer is not willing to come up with structural methods to reduce or mitigate the sexual behavior (such as having male staff perform self care for patients known to be lewd or arranging for more staff to assist so they can restrain/control the patient during personal care) then she may need to look for another position in a different medical specialty or another field in general. If she’s a CNA she hasn’t invested a whole lot of time and money into her education yet, and she should think long and hard about whether or not she wants to go to nursing school.

There is no cure for dementia (honestly even the treatments leave a lot to be desired) and in the end stages the patients are very hard to deal with, both physically and mentally. She should see if her work has an EAP to help deal with the emotional aspects. A common outcome is that caregivers get burnt out and stop treating these patients with compassion and respect despite their atrocious behavior which is a symptom of their disease, not a choice they are making. That does not serve anyone well, and those people don’t belong in medicine any more. I personally don’t have any grandparents left so I always focused on taking really good care of someone else’s grandparents.