Crittering! One of the toughest behaviors to modify in a dog, unfortunately. You'll have to watch her closely. If you see her "get scent" (nose to the ground - or some dogs lift their heads as scent drifts up - very excited motions, obviously looking for something), tell her "NO" in a firm voice, and when she stops and looks at you, reward her with a favorite game or treat. (My dog loves tug of war, so I save for when he does something really good).
Another option if you can stand it, is for at least during baby bunny season, go to a hunting store and get rabbit scent (used for training hunting dogs). You can probably order it on line. Soak a piece of cloth with it, then rubber band/tie it to her collar. Theoretically she should be so overwhelmed by smelling rabbits all the time that she is desentized to rabbits. The problem is that you'll smell rabbits every time you're around her.
There are other ways of training a dog not to critter, but those are the humane ways.