One thing that can't change (if you go ahead with getting another dog) is Domer's routine. Try to add as little stress as possible. Give her (alone) attention time, maybe walk them seperately at first, etc.

The thing with females though, is that they're called bitches for a reason. I've heard that females are the real fighters while males mostly huff and puff (so to speak). My males had a fair number of fights when they were introduced but none were ever really intense. They were all little fights and a lot of growling and standing tall. If you can get them clear on pecking order, it should go smoothly.