Thinking more about your dilemma . . . if you have a doggy food boutique near you, they might have free sample bags that you could ask for to use as treats/supplements for Libby.  Foods like Orijen are higher in calorie/protein density and they give 1 pound sample bags.     
You could also give her scrambled eggs, sweet potato, and some parmesan cheese.     
				__________________  Kristin, Max and Teddy          |