
Hi Dina,
The dog may well be allergic to what she has been fed - even on the changed diets :( For example if she's allergic to wheat, she's been changed away from one diet with this onto a pasta diet. It seems strange advice to add bread to a chicken and rice diet for instance. If it presents as a food allergy, wheat, corn (sometimes all grains), gluten and dairy are usually the first things to remove immediately from a diet

You've certainly advised her well to change vets - I'd not tolerate a vet who didn't refer a case to a specialist vet long before 4 months had passed when he's clearly gotten nowhere

Depending on what your own vet finds and recommends after his/her exam, I'd be requesting a full blood panel within a week if there was no improvement to rule out common causes and specifically request an EPI test too.
Please keep us posted and wish your sister all the best with her youngster - it must be a dreadful worry for her with a puppy having suffered so much for so long.
Best wishes, Teri :)