I am in search of a new addition to bring into my home. I don't have a particular age or breed picked out because when I fall in love, I fall in love! My biggest issue, however, is China. She does not like other animals. She's not attacked any, and when I introduce her to new animals, she's leashed, her treats are in my hand, and I'm waiting.
You "waiting" and being tense and holding a tight lease is doing more to cause this problem than help it.
Often dogs who are aggressive on leash won't be off leash. We all have heard of introducing them on neutral territory but I'm not sure that really accomplishes anything. I suggest getting a dog of the opposite sex. A puppy would also be less of a threat to her.
Usually dog fights aren't nearly as ferocious as they appear to humans. They may have a few in the beginning but its just to see who is the strongest. My suggestion is to take the new dog to the back yard if it's fenced in, then open the back door and let China out. Stand back and leave them alone.
There is a greeting ritual that dogs must go through and you shouldn't intefere. The thing that makes most dogs leash aggressive is because a normal greeting is very difficult while 2 dogs are on leash. They will touch noses, sniff butts, circle eash other, then sniff bellys, then circle some more then they will run off and play.
The more you stay away from this and just let it happen the smoother it will go and the less likely there will be any trouble. Stand back, don't say anything, don't bark orders, just be a part of the background. If one growls, its ok, don't say anything. Just let nature take its course. While they are outside this initial time, don't interact with either dog any more than necessary. After they've spend 30 minutes or so outside, bring them in. Give them both attention.
Usually when introducing a new dog into the family, it will take a few weeks for both dogs to get comfy with each other. There may be some growls and there may be a few skirmishes. Don't let the skirmishes get you upset, they are normal and not meant to injure. The dogs will just be testing each other.
If you get a puppy, the skirmishes won't happen. China will let the puppy get away with murder for a few months and by then they are used to each other.