(((hugs))) I think you did the best thing for Ada. I know it's not easy to have a dog who hates your other dogs. Before I joined Chaz, in the Before Benji time, my family had a dog who after living with us for three months decided she wanted to kill, and I mean kill Daisy. It wasn't fair for Daisy to live in her own home in fear, and it wasn't fair for the other dog to be so upset all the time that she felt the need to attack Daisy for (to us it seemed) no provocation. That dog went to a rescue who found her a good home.
Heck, I moved into an apartment with friends where I'm happy, and left Daisy with my parents where she is happiest. Looking out for your dog's happiness doesn't always mean keeping them with you.