http://www.yorkietalk.com/forums/gen...rn-yorkie.html
This is another great thread where-in genetic testing is being done
You might find of interest post #22 onwards, as well as go to the last page and find out what research can and can not tell us.
In summary your friends' breeding pair
should never be bred again together.
And she would be highly encouraged to do the genetic screening on all her breeding animals to see which of her stock carries the Color Dilution Alopecia gene.