If it's an S-rank mission without much fighting, she might be able to. For example some region pestered by a magical plague that kills everybody, including any mages carelessly approaching. In such a case it would be extremely dangerous and deadly, yet no matter how tough a fighter the mage was, it wouldn't matter. Only brains and certain kind of skills would. I suppose such missions could be rare, and most extremely difficult missions not requiring fighting wouldn't be S-rank at all because trying and failing wouldn't be fatal.