So sorry to hear things didn't work out, but you are doing the kindest thing as dogs who tend to fight tend to live in a stressful situation. To answer your question, you can do some screening by interviewing people and asking for an adoption fee so to discourage her from going to the wrong people. You can contact rescue groups, especially those catering to your dog's specific breed if your dog is purebred. You can ask help from family and friends. Sometimes, you can get lucky and find some acquaintances willing to adopt. Local feed stores sometimes allow you to post ads on their bulletin boards. Last but not least, make sure you let them know your dog hasn't been getting along with your dog so that your dog is placed in a new home where she can relax as being the only dog.