I wouldn't necessarily suggest this except in cases like yours. Have you tried letting her have whatever she wants, like people food? When you eat does she want what you have? Cane has 3 foods that he never turns down. Real butter, real cheese and coconut oil(solidified). Try different things and see if there is something that really turns her on. If you find something that turns her on then use it to entice her to eat. If it is cheese, wrap hunks of chicken in it. If its butter stuff some chicken hearts with it. The problem with this is you could be creating a picky eater but it sees you already have that problem. Some dogs, just like people are just naturally skinny. My ex could and did eat more than most men twice his size he never gained weight until he hit about 35.