Has something happened in her little world that may have provoked this behavior i.e. work schedules changing, new addition to the family, being left alone longer than normal, lack of excersize? Seems like she's frusterated with something, or maybe has been "ruling the roost" for too long?? BTW- how do you NOT let the yorkie rule the roost??????
Maybe a re-run through an obediance class would re-establish your pack leadership???
As far as the grooming, my Ranger was combed daily from the second I got him. After a few weeks he started getting nasty and biting me, the comb, the nail clippers, etc. My dog trainer told me to lightly grab his little cheek, look right into his little eyes, and tell him to "knock it off" in a mean tone. I didn't want to do this cuz he's so freakin' cute, but with his naturally dominant behavior, I figured I had to try it. It took one or two nastys and he hasn't had any issues since, and it's been four months.
Good luck and keep us posted!