That sounds like her teeth may need to be floated. Do you feed her on the ground? Have you noticed if she drops a lot of feed? It is very possible she is getting the grass stuck in between her teeth and her cheek. That's what my old guy does. He actually has very few teeth and will chew his grass or hay into a "cud" and then spit it out.
"Be a best friend, tell the truth, and overuse I love you
Go to work, do your best, don't outsmart your common sense
Never let your prayin knees get lazy
And love like crazy"