Slippery Elm is a great suggestion and may bring her some good relief. I've also found that the throat has to do with expressing oneself. If there is something she feels she needs to say to someone, but doesn't, the energy can get stuck in her throat and can worsen until it is released. I rid myself of many sore throats, even strep throat, by intentionally expressing what I felt needed to be said. Also, creative and artistic outlets help immensely. She will benefit greatly by letting her voice be heard.

Sending prayers and well wishes to you and your mother @bien. Giving you my 100% upvote as well. Blessings on the way.