L.M.
My son did that too, she's just looking for something hard to bite to give her top teeth some relief. Once the teeth come in she'll stop. You can try to give her other things to bite, but my son never liked teething rings. He did like to bite his sippy cup and hard plastic toys (and most recently my iPhone that I keep having to keep away from him)...
Teething is a tough time, the molars are the worst. Hang in there!