Garyf, you sound disappointed, but please don't give up on this girl. Regardless of her size and looks, she is yours now, and will give you a lifetime of unconditional love and companionship. My Yorkie was the hardest ever to potty train. I had pure Schnauzers before, and they were so much easier. Give her time, and be diligent in your methods.
Even pure Yorkies vary in appearance, as you can see in photos of all of ours on YT.
Here is a link to snorkies, so you can see how they vary also.
Snorkie, Snorkies, Mini Schnauzer Yorkie Hybrid