Baby LOVES chewing on metal..why??

It almost sounds like she started chomping metal more because of teething and the coolness, hardness of it and then it just became an obsession. Drug exposure does seem to have that OCD/sensory component to it. I'd try to maybe feeze one of those teething toys and offer that to her to get her onto something more appropriate. A good children's multi vitamin wouldn't be a bad idea in case she's deficient. If it's possibly yeast related, a sugar-free diet really helps to keep that in check. Curcumin, grape fruit seed extract, and garlic are awesome yeast fighters as well.