THANK YOU FOR REMINDING ME AND RIDING MY HEART OF UNNECESSARY UNEASINES, BLESS YOU
Wait I forgot, what necklace? And what does it do again?
I just checked and it seemed like the necklace was for poison ("universal antidote")? how would that help with being harmed from a spirit's attack?
SPOILERS though everyone's already kind of spoiling things so if you're reading the comments right now you're already kind of in trouble.
Charm, when the prince prevented the epidemic that Bertia told him would kill her mother, he also gave her the necklace she is wearing full of a 'universal antidote'.
but why, I thought of that, but being hit doesn't mean the result is necessarily magical. Not sure on that. It just doesn't make sense to present such a useful item that Bertia has been wearing right along and not have it used by the end of the story, and if she was the sick one using it on herself then it wouldn't be as special as using it on the very prince who gave it to her. I guess I'm speaking more as a writer than a reader with that kind of logic, though.
It's okay guys she's got the necklace