It really is just not worth taking the chance of breeding her, there are just too many things that can go wrong. With larger
dogs the risk is great enough, but with the tiny
dogs, the risk is SO much bigger! Please, do your dog a favor and talk your mom out of wanting to breed her. Have your dog spayed, and if your mom wants another puppy, buy her one either from a responsible breeder or adopt one for her from Yorkie rescue.