Give her a detailed list of all the expenses required for whelping a litter of puppies. Its not cheap and its not easy. And you won't make a ton of money doing it.
You must take the mother (dam) in for regular checkups to make sure her litter is developing correctly and nothing is wrong.
You also need an ultrasound or an X ray at the right time in her pregnancy so you know how many pups to expect.
You need a whelping box for the dam.
You have to take the dam to the vet right after birth (that is, if it goes well)
if there are complications, you may need to see an emergency vet (expensive) and get the dam a C-section (also very expensive)
Then you have to have puppy food, dewormings, vaccinations, puppy pads, spaying or neutering.
and after all that, if the dogs have no pedigree of any kind, they are worth about $50.
Also ask to take your mother to a shelter. then ask the shelter workers to show your mother the euthanasia room, since most of those puppies will also be seeing it....and not leaving alive.
The chance of those puppies getting homes that will keep them past 2 years is slim to none...they will likely end up in a shelter before they turn 2 years old. They have only a few short days to find a home before they are put down, or they get sick and have to be put down.
for every thousand dogs that get dropped off in a shelter, seven walk out alive.
Show her these answers. There is no money in breeding dogs. or any animal.
And if she doesn't get the required vetting done and sells unvaccinated puppies. She could be sued and reported to the SPCA for selling sick puppies.