[JoeyP]

You're definitely dealing with a dominance issue
but dominance doesn't always mean Aggression
Your Yorkie is showing dominance ... but she's also showing aggression as well
and that's what needs to be stopped
the growling and biting need to be corrected immediately
if your Yorkie growls and bites when people leave set that condition up
have someone go to leave the room
The minute your Yorkie goes to growl or bite
You need to be there to correct
EH! and a nudge
Make sure she listens to you
watch their eating ... are they growing at each other during mealtimes?
over toys?
use these instances to get a handle on your Yorkie
one always has to be dominant
but that never means fighting and biting