You can have your mom go to
http://www.petshoppuppies.com to get a report on where her dog came from. But she was almost certainly lied to. No responsible breeder would allow their dogs to be shipped off to a store (especially another state) and go to whoever can fork over the money. A responsible breeder will do reference checks, a home check and interview you. Her paperwork will say who the breeder is. You can check to see if the breeder is listed in the USDA's list of "licenced breeders" although that list was last updated in 2003. That list of class A breeders can be found here:
http://www.aphis.usda.gov/ac/lists/lista.pdf and the list of class B breeders can be found here:
http://www.aphis.usda.gov/ac/lists/listb.pdf
Also, a puppy mill is a slang term for a commerical breeder who cranks out a large quantity of dogs in poor conditions. And the more dogs you crank out the harder it is to provide clean, healthy conditions, proper care and socialization. And, the less they provide for the dogs, the more profit they are making. So, just because they send in their fees to the AKC to get "papers" doesn't mean the dog is healthy, socialized or worth the $1000 you're paying for him/her.