I've rescued emaciated dogs that took just 8 days to plump up and I've had some that took about 3-4 weeks. I would have her checked again for any internal parasites and given her condition, it doesn't hurt to take a dog like that to the vet every week to monitor her progress. I would get a copy of her medical records from the vet who was mean to you and take them to the other vet also. What does her stool look like? Is it formed and firm or is it softer than it should be?