Snitty, when I had my dog in agility there were a couple of dog aggressive dogs in the class. We would just crate the dogs with a blanket over the front so that they could not see the other dogs running the course. My dog would get extremely excited when a Border Collie in the course. I'm thinking because he was really fast doing the course and her pery drive would kick in. But when it was her turn to run the course, she had no interest in the Border Collie. If you can find a course in your area that has good safety practices, Bella might have fun giving it try.