Year of the Dog

I recently adopted two dogs. One, a black lab I named Rosalee. She and her companion, a mutt named Ralph, appear to be about two years old. They are cute and cheerful and full of energy, but Rosalee attacked my cat Poe, the QUEEN of our domain, right before Christmas. So, I found myself with a big problem- what to do with Rosalee after she caused my cat to need twelve staples in her belly. At first my reaction was to get rid of Rosalee- send her back to the pound. Then, I relented. I realized that I had already fallen in love with her. I also realized that it would kill me to send her back to the pound. So, now we live in a precarious bliss- the dogs out only when Poe is inside, and Poe outside only when the dogs are in their big 20 X 20 kennel space. It works, but it isn't always easy. This situation makes me yearn for a time when the dogs and cat can peacefully coexist outside. I dream of one day being able to leave them all out, unattended for long stretches of time without violence. I have asked people more versed in the way of the dog and been told that Rosalee needs behavioral modification. I am skeptical. I do not have a lot of free time what with teaching at two universities and writing a dissertation. If anyone has advice I would appreciate it.