It sounds as if she wasn't able to shed the old skin off them properly. (like Merlin said) The humidity in her house needs to be increased, and she would benefit from baths. I don't know if they will grow back. It depends on how bad the damage is.
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Were the spikes black before they were lost? If so this is a good sign of retained shed and lack of blood circulation resulting in the blackness and spike loss.
Harnesses are huge culprits of lost spikes as well. Many of us here use a hind-end leash instead. It greatly reduces the risk of spike dameage and serious damage to your igs neck and throat if it decided to alligator roll.