The first reason, as Sarita said, is the risk of cancer. Female rabbits have an 80% chance of developing uterine/ovarian cancers by age 2 if not fixed. You don’t want your bunny dying of something easily preventable.
If you were to ever get a buddy for your bunny, both would need to be fixed, otherwise they won’t get along.
Even if she does not become destructive now, later in her life, she may. The problem with that is it is much more dangerous to spay an older rabbit, it’s easier to do when they are younger.
The last reason would be to avoid pregnancies and false pregnancies. If your rabbit was ever to come in contact with a intact male, she could easily become pregnant. Pregnancy is very stressful on the rabbit and there are already too many rabbits in shelters. Intact females can also have false pregnancies where they think they are pregnant, build a nest, etc. this can also be very stressful on the bunny.