Thank you for your question. I forwarded it on to our in-house veterinarian staff and here is a response from Dr. Holly Nash, DVM, MS:
It is quite common for reptiles to eat their substrate (bedding). I would monitor your bearded dragon closely to make sure she doesn’t eat rocks outdoors and also that she isn’t eating her substrate. This can lead to serious intestinal impactions and even death. I would recommend paper or Astroturf for her substrate. The exact cause of this behavior is unknown, but I’d make sure she is receiving adequate calcium in her diet and also adequate UVB light. Our article on bearded dragons may be helpful: http://www.peteducation.com/article...
. Good luck with your dragon! -Holly