Hi there JCat,
Cats are VERY territorial. Basically they view any other cat as a huge threat because they can steal the current resources (food, shelter, napping spots, etc.) that are available in that area. In that case, a new cat who is introduced to your cat's territory can use and lessen the available resources; in the wild this is a matter of life or death, cat's will kill over territory and resources. So, it is perfectly normal that your kitty wants to destroy other cats that venture into her territory. Dogs on the other hand, since they are a different species, do not threaten cats nearly as much. Dogs also eat a different diet, sleep in other areas (on the ground, where as kittys prefer to sleep up high), and don't mind sharing their shelter since they have a pack mentality, so resources are not as threatened as where they would be with another cat entering the territory. Hopefully that helps make sense of your kitty's aggression toward other cats and her welcoming acceptance of dogs.....although that certainly does not rule out the fact that she might have been a dog in her past life too.