Hi,
She requires a diet which will provide energy and at the same time boost her immunity. If she doesn't have denture problem, she can able to eat semi solid diet to solid diet, because through the liquid diet all requirements can not be meet. Better you prepare one dish meal with soft texture that will be easy to digest ex: khichdi ( masoor & moong), soft poha, vegetable broth, curd rice, soft fruits like papaya, watermelon etc. Try to give small portion at a time instead of large meal.
Health Tips
If possible make her indulge to do little activity which will improve metabolism and function of vital organs.