Here's the thing -- The main reason behind spaying female rabbits has to do with the risk of ovarian cancer. It seems that ovarian and reproductive cancers are very common in female rabbits that do not breed. Spayed females appear to have a reduced chance of having to deal with this.
HOWEVER, the surgery itself is often dangerous as most small animals do not respond predictably to anesthesia.
If you are considering getting your bunny spayed, I would first check out vets. If you cannot find a vet who has performed the operation more than a couple times with a high success rate, then you may be better of leaving her unspayed.