It definately looks like a full bred chocolate yorkie to me but if she can't come up with pics of the parents run as fast as you can. I have pics of all 5 of my breeding dogs. Not necessarily really good ones but pics none the less!
And I get a lot of flack because they aren't all chocolate in color, but carry the gene. But this one looks like my little female that I have left and I will gaurantee you she is all yorkie. The only other breed I have is a boxer for my yorkies protection when they are outside in their yard!