I'm a dental hygienist. Biotene makes rinses and other products especially for people with dry mouth and combat that and bacteria. Go to Biotene to see the products and ingredients. They are alcohol free. There is even a spray to use throughout the day. You do not spit that out. It would not hurt to swallow small quantities. A better resource to ask is a dentist not an M.D. As they know very little about the oral cavity. I'm curious why you want her to use a mouthwash? I agree that a too there could be dipped in the abiogenesis and swabbed in the mouth or use the spray.
You should never swallow mouthwash. Instead, nursing homes and hospitals use little swabs (on a stick with a saturated sponge on the end). You just hold the stick and wipe it in the mouth and you don't need to spit it out.
The swabs are great as ferris mentioned. If you are worried about bacteria you could put warm salt water on the swabs. My dentist told me when i had a tooth pulled that warm salt water was the best for healing and he was right. I did not swallow it so if you used with swabs it would be best.
Coconut oil is edible, has anitbacterial & antiinflammatory properties...I use it to brush my teeth and swish in my mouth...can be swallowed & works GREAT!