First of all, you need to identify precisely what the problem is:
How old is elderly, Dixie? Has she lost her front teeth? Has she lost any back teeth, all back teeth or does she have an infected or overgrown back tooth/molar? Without risking your own fingers, you can run a hand over the outside of her cheeks to feel any sharp bits of tooth sticking out to cause pain and any gaps, or to see if she reacts to pain when you touch a tooth. Don't ask me how many molars they have, but it's 'some', perhaps 3 on each side? Everyone knows how to check front teeth for missing or wobblies, but molars are often overlooked.
As Shep53 says, don't put your finger in her mouth to check back teeth, as you won't get it back! Sheep have very powerful jaws!
Our most recent elderly ewe, Zanfara Elfilda, Elfi to her friends, finally died last week at 18. She was blind and had no front teeth, but she had enough molars to chomp on 'Tup and Lamb' coarse mix every day. She could rip grass without front teeth and chew it with the back teeth. Her favourite treat was pieces of digestive biscuits (McVities only!) but unfortunately that is also the favourite treat for the rest of the flock, so Elfi was always fed alone. In fact being blind, she preferred to have a tiny paddock to herself, with the Crow family and our JRT as her friends, as the other ewes would knock her over. She lived like this very contentedly for several years and maintained surprisingly good condition. It was a recent storm that finally got her. As an occasional seasonal treat we would feed her cow parsley shoots, holding them in our hands so she could rip them against resistance. She would also eat willow leaves sometimes. Elfi did eat hay. I think perhaps your ewe has a wobbly or perhaps an abscess which makes pulling or chewing hay painful. Often it's best to remove a wobbly front tooth to allow the animal to pull grass. Once it's really wobbly, just lift it out and she will start eating again within hours. If it's an abscess on a molar, she will need antibiotics. Once a ewe starts to lose teeth, we opt to not breed from her again, but she is welcome to end her days here.