So, if she has no magic resistance, why has no one hit her with petrify or ko, or something else along those lines.
To be fair, I believe the story established that Goblin's usual stomping grounds is one for mostly newbie adventurers. If this series uses the established RPG ailment spell tropes, that things like petrify or death would be mid to late tier spells newbie adventurers wouldn't have access to. Sleep, especially a single target sleep, is generally an early game spell.
At least if my knowledge of classic Final Fantasy is anything to go by.