Past 6 weeks at dinner chews food (mostly meat) & spits it out. has some of own teeth. She eats her breakfast and lunch. She will eat a sandwich or hamburger for dinner but isn't eating her full dinner. She has been an insulin dependent diabetic since 1967.
Jeannegibbs, above, had a great idea about milk shakes.... even Carnation Instant Breakfast stirred into milk is good [depending of the sugar content].
Oh, I found some info on the chewing and spitting out from other posters. https://www.agingcare.com/questions/part-of-dementia-to-eat-and-spit-out-food-156999.htm
When my husband was in a tcu, one woman "ate" a complete meal by chewing it and spitting each mouthful into a glass. While this is pretty disgusting for others to watch, it is apparently not unheard of. Give Mom a sturdy disposable cup or glass to spit into if she must. Don't make her feel bad about doing it. But work on finding things she might be able to eat more easily in the evening, and reduce the portion sizes so the meal doesn't seem overwhelming.
At 94, Mom's experiences should focus on Joy and not on "good" behavior. Unless she is losing weight, I wouldn't worry about her not eating a traditional third meal for the day.