6 weeks is too young to be away from the litter, she shouldnt leave momma until she is at least 12 weeks old.
Just the fact that they let her go too young, she smelled and had fleas proves they are NOT reputable breeders.
Really she should go back to her mother until she is 12 weeks old, but it dosnt sound as if they are taking very good care of these pups if they would send her to you in this condition.
I brought my Poppy home at 6 weeks and it is very scary when they are so small.
Its good that she is seeing a vet but a vet cannot tell you much at this young age as somethings dont rear their head until much later.. but for now a vet check is the best you can do.
You need to keep a close eye on her as these little ones can go downhill quickly.
You need to rid her of the fleas and make sure she is gaining weight, you will get a lot of help and support here at YT. Good luck.
__________________  Rachael & Poppy |