First its NOT a breed - its a mutt - and a pricey one. Sad to say your mom was ripped off by the pet shop.
I do know that small breed dogs tend to take a lot longer for housetraining. You need a crate to keep the pup in till it can be trusted. I'm sure the pet shop was not good about shots, health, etc. Most pet shops get their animals from mills or backyard breeders with little socialization. Many have health problems.
I'd take the pup to the vet for a complete checkup, blood tests, and shots.
I do know that small breed dogs tend to take a lot longer for housetraining. You need a crate to keep the pup in till it can be trusted. I'm sure the pet shop was not good about shots, health, etc. Most pet shops get their animals from mills or backyard breeders with little socialization. Many have health problems.
I'd take the pup to the vet for a complete checkup, blood tests, and shots.