You can breed her as often as she is receptive/willing. Which could be two or even three times a year. It depends on the animal, and whether or not you care about her health, longevity, etc. and that of the resulting eggs/hatchings. If you want her to live as long as possible, might be best to never breed her and do your best not to have her start laying eggs in the first place. Breeding an animal less than once a year wouldnt be unethical IMO.