I am going to put something out there that may sound crazy to you but it sure is worth the effort of researching. Leaky gut syndrome. I was watching Dr Oz....I know, I know...but he was disussing this today and with a quick google I noted that dogs can have it too. Diet is one of the things that helps along with some homeopathic remedies. Worth checking into since your pet is so yooung and your vet does not want to do some tests because of her age.
ALSO, welcome and do you have some pictures that we can drool over???
It Is What It Is