She looks adorable! And VERY much yorkie!
I think she will be a very healthy big yorkie! Ig she gets over 12 lbs she could be what you call a silky terrier - looks ezactly like yorkies but are bigger.
The dog to the right looks like it has something mixed in it - maybe scotch terrier or something, but that could as well be the cut. But scotch terriers are bigger than yorkies, so that might explain her size.
600$ for a cutie like that is a very fair price and I hope you'll love her as much as the rest of us love our dogs, pure bred or not