Welcome to YT
The mom looks like a yorkie but, I have seen many Morkie's (Maltese, yorkie mix) that look just like a yorkie, in fact one of my neighbors has a female Morkie and a male Yorkie and they look exactly alike. Morkie's are
not a breed, technically they are mutts, in today's society they are called "designer or hybrid" dogs and sell for $2500. and over. The only way you will know if the mom is pure yorkie is asking to see her AKC papers same for the sire. If this breeder is reputable she will have the papers, if the breeder is a back yard breeder she may not have any AKC registration papers on either of the dogs.
If you decide to buy the puppy you can have a DNA taken for your own piece of mind for $85. to $100. at
www.wisdompanel.com
Good luck