Memysel3, it sounds like your vet is treating conservatively at this point, but only the bloodwork will truly reveal the extent of the problem (or specific liver condition, there are various types, each requiring a different treatment approach)
In HL, initially, a high calorie, high protein diet is preferrable to help regenerate the liver (as Misha noted, Hill's Rx A/D is ideal for HL nutritional support)...once the initial crisis is resolved and kitty is eating on her own, then a maintenance diet of low-fat, low-protein is usually recommeded. In other liver conditions, the diet may not be as important, and in Wendy's case, I can see how your vet would recommend any type food for now, on the premises that she is so malnourished. A couple other things you might attempt are Nutrical or Clinicare, both supplements you can use in combination to the diet. Kitten food might be ideal in her situation for added nutrients and availability of those nutrients, caloric content, protein content etc, but again it depends on the specific liver disease.
Here's hoping Wendy continues to improve and that bloodwork reveals more normal liver function. Keep an eye on her hydration status, check for signs of increasing jaundice, urine output, stools, and if she develops vomiting problems, don't hesitate to get her back in promptly..................Traci