My Westie

My westie is almost 11 mos. old. I got her when she was 8 weeks. I have a teacup maltese and a regular maltese dog. The maltese dog is 16 years old and has always been the alpha dog. The westie seems to get into fights with her ocassionally. The other day I had seen the worst.First of all, rawhide bones had been bought for all. No sooner did the teacup go after the rawhide, the westie fought with her, for the first time. My mother tried separating them only to pick the westie and in her mouth was the teacup hanging. She didn't puncture or bite her really hard. But it was devasting. The other maltese was only walking towards the rawhide when the westie attacked her. Trying to fight back, I pulled the westie off of her only for her to slip out of my arms and make a made dash for her again. She fought her making the maltese defenseless and screaming. I finally got her off and the maltese was limping on her leg. I immediately put the westie in her crate for fear she might do this again. I only took her out when the others weren't around. I got in touch with a westie rescue in hopes to find her a good home. In the meantime there is a couple that's interested in her and she will be spending a couple of days with them to see if she acclimates to the new surroundings. It's heartwrenching for me, because I adore the westie. She's lovable, fun, energetic and has her own personality. My question is, what could I have done to prevent this from happening? How do I separate two dogs that are in attack mode without each harming the other? I was told by the westie rescue that the females are very dominant. If this couple do not want her, I'm almost tempted to keep her. All my dogs are females and two maltese dogs get along great.

Thanks for your help.
Chloe