I've seen little bully's, but generally they aren't healthy. Some breeders want what they call t-cup bulldogs. So the inbreed small bully's . What happens is the bad unhealthy traits go with the pup, just like breeding for specific colors.
Please get another vet to see her. How's her appetite? does she like to eat? how's her poop? is it normal? regular, formed? twice a day? does she seem to be thirsty all the time and drink way too much water? please keep us posted