The question isn't whether or not she can bite through metal, but whether or not she can bite through whatever metal Nac's characters are comprised of. Not all metals are the same after all. Not to mention you've got an angry body trying not to get gnawed on under that metal.

*poking at Amber playfully* Well well, look who finally hit that growth spurt! Pushing six feet now are we?
Jacque: Shade...that ain't a good idea.