hmmm... I don't really have any personal experience in this area. I know a lot of people recommend baby food, but when I read the labels they don't seem to be too high in fat or calories...?? I've seen a lot of people recommend Pediasure, Ensure, Boost, soy baby formula... anything liquid with a lot of calories and nutrients she can take. There's a paste all the rats love that's very high calorie called NutriCal or Nutristat, which is usually in the ferret or cat section (even puppy section) of most pet stores by the hairball stuff. Usually 6-10 dollars -- about the size of a tube of toothpaste.
You're probably better off getting her in earlier rather than later to the vet, when it's way beyond helping. Maybe some prednisone and/or antibiotics can help. I probably shouldn't say this, but it doesn't sound very good. Pituitary tumors can't be operated on, but I believe you can extend their life and alleviate their pain through medication for some time. I can't find much on it, tho. I hope someone else can give you some feedback.
Also, if it is kidney or liver degeneration that would be totally different meds. For something so serious, she really does need a vet. Good luck with your girlies.
heh heh -- modified to say tube of toothpaste, not tub!