What's wrong with my bird's beak?

My cockatiel's beak grows too much, her beak grows almost to the bottom of her head and her lower jaw is growing a bit too. We have a cuddle bone in our cage that the other one chews on, his beak is fine. But she chews it a bit and her beak still gets longer! Her jaw has even shifted to the right from all the extra beak. Does she have a calcium problem. Please answer.