I thought it was an odd title!! definatly got my attention. lol :D

muzzle
 

After one of my had her babies she took to attacking her former best friend...viciously ( i knew she was in protect mode ) despite knowing she felt she was protecting her babies it was going on so long and so viciously I knew I would have to re-home the one or figure it out. I believe I contributed to the problem by keeping the other with my son most of the time when the other was having her babies and for the first couple weeks.
I got a soft mesh muzzle for the aggressor and introduced them, much to the muzzled one's surprise there was nothing she could do. Kept them separated as much as possible for a few days, introduced them several times a day - always with the muzzle on. Later we'd put them together carefully without the muzzle, at the first sign of aggression, on went the muzzle (only for a few minutes/then taken back her her babies in another room). Finally, she figured it out...be nice or get muzzled. Thank Goodness she's smart and everything's fine now. They stay together all day without any issues.
So you might try a muzzle with the aggressor...just don't leave it on too long, just so she gets the point that you're in control and have a method to keep her in check.

I might add that anytime she gets aggressive in barking at someone, whatever, we just say "Do you want the muzzle?" and she immediately stops her bad behavior (& goes and lays down in a pout).

Everyone told me that walking your dogs together will help them to bond. Couldn't hurt; unless they fight while on the leash and you have problems controlling them.

Perhaps someone could walk with you and each of you walk one?

Victoria Stillwell did episode on a chiachua and a yorkie who would fight the way your two bitches does. What she did was everytime one of them started to attack the other, she removed it from the room. When they were in the same room without fighting she would reward them. Eventually both dogs started to associate fighting with being removed from the room and they gradually stop fighting. The other thing she did was to give each dog individual time. It was amazing to see these two little dogs go from angry aggressive little pups to at least being able to co exist.

It took her a long time but she finally was able to stop the two from fighting and they were eventually able to go out on walks together. Patience and persistence was the key.

Oh my goodness. I just learned something. Bella's previous home was being shared with another female. Bella wasn't spayed. I bet the other little terrier wasn't either. Previous owner kept them apart. Not social with one another at all. I going to say this tho, because I've seen it on tv. I think I would walk each seperately but then one of the walks together. I would think that would help and keep them busy at the same time. Could be wrong tho.

LOL. you are going to laugh, but the only thing that helped my two spayed females from fighting was. . . getting a 3rd yorkie: A MALE.

.. I NEVER TRUST A FIGHTER...did Victoria have to pry the teeth out of the flesh of each dog...leaving a bloody hole..sometimes it is an ear, sometimes a leg.. an injured eyeball...that needed the eye dr vet!!!!
Was her finger or hand in the way and had a Yorkies teeth sunk into her skin?

I had two girls..Charlotte and Ruby who HATED each other... they had two bad fights with me standing right beside them....so they were put into two separate parts of the house...6 full months went by, they never laid eyes on each other...soooo I think surely they have forgotten the feud...Charlotte walks into the room and Ruby came in from the other door..both walked through a group of about 6 Yorkies, straight to each other and a death match was on...they were never allowed together again for the rest of their lifes...

I think the dog behavorist is a great idea. But for sure you want to make sure that this aggression is not a general aggression to other animals. Dogs with aggressive temperaments quite simply should not be bred.

And as YorkieRose said sometimes, for what-ever reason(s), two bitches spayed or unspayed just won't ever ever get along. BTW it can also happen with males; neutered or not.