There are A LOT of ways to deal w/ this.
One of the easiest is to give Miss High & Mighty Maggie fewer things to feel the need to get pissy over.
For example, her bed? Yeah, she doesn't get it anymore. Or if it's down, it's in an uncommon room.
The food? When you're dishing out the kibble (all dogs in the same room) I'd have Maggie on a leash w/ either a harness or a collar (especially if she's a Yorkie within the higher end of the standard) and give her a correction if she even growls at any of the other dogs and then feed her last for awhile, but have her with you when you're dishing the food out so she might be tempted to miss behave. Teach her that's simply not how things are going to go down in that house.
She needs to learn that you're the one that she should turn to if she's having issues, not lash out on her family members and be a brat...it makes for an uncomfortable life for the other dogs too.
Like my signature says, "Big things come in small packages" and Yorkies are awesome because of this, but sometimes these little terriers can develop a big head.
If there is an over abundance of toys or one specific toy she gets more posessive of, take it away. Or have her on a leash while you play w/ her while the other dogs are in the same room or nearby so that you can give her a correction if she shows any aggression. A lip curl, a snarl, a growl....even a dirty look or freezing up.
Feel free to e-mail me anytime for more options.
topsredhead@yahoo.com