Sooooo many good answers have been given. I would think that the temperature of foods may be important as well. Very cold things like ice cream may cause pain, while a cool gelatine desert would be soothing. In the same vein, I would avoid very hot foods, opting for comfortably warm.
For nutritional value, there are whole grain cereals such as oatmeal and farina (cream of wheat). Bright veggies that can be cooked and mashed are easy to eat. Examples are sweet potatoes, beets, rutabegga, etc.
Of course soups are a natural and are highly nutritions if made properly.
For meats, go with foods like canned tuna or salmon, mixed with mayo, mustard, and onion powder, and maybe a touch of dill. Pate's are good, if she likes them, as are sandwich spreads such as deviled ham, potted meat, and ground up bologna, when flavorings are added of course.
And as was said in a previous post, fruit smoothies are great. I add carrot and firm, silken-tofu to mine, to add nutritional value. I omit the ice. Some fruits you can mix and match that go very well in smoothies are cantaloupe, peaches, appricots, apple, pear, pineapple, cherries, most berries, papaya, guava, banana, anything that will blend smooth. You can even add such things as psillium husks to a smoothie to increase the fiber content.
And it's hard to beat a good shake or malt, or even a glass of milk with a touch of butterscotch, or chocolate flavoring. And then, there's always eggnog, served warm or cool, with a bit of nutmeg on top.
Hope this helps.
Seeeeeeya;; Goodweed of the North