Hi S.,
I would say that the baby is just trying to help those little teeth get through her gums. When my grandson was that age he would even try to chew on table and chair legs, just like a puppy! He is now 16 months old and although he is still teething, his front teeth are all in, so he no longer bites everything is sight.
Babies R Us carries a "gummy" style crib rail cover that will allow her to bite without chewing through to the wood. And like others have said, give her other things to chew on, and keep an eye on her when she is crawling around to make sure that she doesn't do any damage to herself.