Have her try giving up dairy for two weeks to see if it helps her arthritis. She can go back on it if it doesn’t, but it’s a small sacrifice if it does. My mother just recently went off dairy and the pain in her arthritic knees has stopped and she’s able to get around a lot better.
Do a Google search on dairy and arthritis, it’s the highest ranked food for causing arthritis/join pain.
May consider some Co Q-10 too.