Overly dominant females

Last night i tired adding a new rex haired female to my original group of 3 females. One of my older females is insanely dominant and beats up the others if they step out of line. So she killed my new female only a hour after i put her in the cage...
I tired introducing them all first outside of the cage, and the other two didnt mind her at all. But once the dominate female started attacking her the other two jumped in!
Its really getting annoying. The friend i got got the rex from hasnt never had a problem with introducing females, and neither has anyone i talked to who breeds mice, its just males that give everyone problems..
Has anyone else experienced this? Or does anyone know what i can possibly do to fix this problem preferably without have to kill the psycho female? If worst comes to worst ill probably just kill her but id like to see if maybe its me whos doing something wrong before i kill anyone

Melody, I've bred rodents and I don't know of a single fix for that situation except individual housing, which can be expensive. Some females are just like that.

I'd feed her off and replace her with another breeder if I didn't have the space to house her by herself.

The easiest thing would be to cull her off, and replace her.
Another option is to try housing her with different mice, until somebody is more dominant than she is.

Also, you can try putting a drop of pure vanila extract on the nose and rump of each mouse in the cage, and the psycho girl, and re-introducing on neutral (clean bedding) territory. That's the more complicated way of doing it, but if that doesn't work then you're :cens0r::cens0r::cens0r::cens0r: out of luck! :P