It seems I can have Corlixia's bones be bullet proof to a point. :P

After writing a bit where Cor gets shot, and the bullet stops just
beneath the flesh, it would seem her carbon nano tube woven
endo-skeleton would be able to top small arms fire. Not sure how
well it would fair from large caliber ballistics like some sniper rifles
in story, and I doubt that they would stop railgun and coilgun
bolts. But 10mm assault rifle rounds and 15mm pistol rounds will
definitely stop, so long as they don't hit anywhere that is not boney.
Doesn't mean that getting shot doesn't hurt any less, just less likely
to puncture most vital organs.

http://news.bbc.co.uk/2/hi/science/nature/7038686.stm