The vet was today and by her check, Persephone is doing okay. She seems to be perfectly healthy, and we're hoping the vomit was a case of being too full, or the mouse sat funny with her. Little worry from the vet for it being a parasite or worm.
Since we're feeding everyone else on Friday, we were given the go ahead to feed her and keep a close eye on her for the next few meals. If for any reason she shows to be sick again, bring her back in.
Thanks everyone for your advice!! :)