I agree with the critiques given. Her eyes should be the focal point, but because her eyes are naturally dark already, adding some lighting (whether reflected, flash, or facing the light as Moab Man mentioned) should help draw more attention there and bring out more detail.
I had to look up the difference between your type of dog and a Yorkshire Terrier. Sounds like yours is slightly larger. We have a Dachshund/Yorkie mix that was a rescue. Her back knees easily dislocate, but she still tries to be as active as she can.
I hope you are paying your model well!