Being social animals, the best combination for keeping rabbits is a neutered male and a neutered female together. So it may be worthwhile considering having your female neutered. Discuss this with your vet. The behavior may also be more dominance behavior than sexual behavior. Many people have witnessed rabbits behaving in such a way towards guinea-pigs for example. Try to closely identify what triggers the behavior and what exactly happens, and then discuss this with your vet.