Sorry HB new to this thread and should have read it properly, I see your dilemma now.
Adding Hellmans mayonnaise with mustard ( or regular) to the mash will make it tastier and adding grated cheese as a topping.
There is Complan that you can buy, you could make it tastier by chocolate, does she like Horlicks or malted drinks they have added vitamins.
Home made soups have been suggested, in our part of the world we can buy vegetables already diced ( they call them Pot Herbs) from the Markets.
I buy them add extra ingredients and stock, simmer for 2O mins add a little butter and then use hand blender.
Though as you say things are inclined to go straight through, so only blend a little so there is still bulk to the soup.