Look for ways to increase the calorie content of whatever foods she does eat. Add fat to her diet, cook with butter, olive, avocado or coconut oil.
Heavy whipping cream in her coffee or tea. Pears or peaches in cottage cheese and add some honey and hwc to it also.
Bacon and eggs with avocado slices. Or sausage. Chicken thighs instead of breast meat. Salmon and tuna.
Straight mix a 1:1 honey with olive, avocado or coconut oil and give her a tablespoon 3-4 times a day.
And let her salt her damn food all she wants.
If she has no appetite she might not want those delicious things.