I feel like Runoa made a wise choice by not associating too much with Demeter and her familia. If Demeter sticks quite strictly to her role as a harvest goddess and her familia members also concentrate on it (some dungeon exploration notwithstanding), other, more ruthless familias likely would leave her in peace, simply because she's uninteresting or irrelevant for them. But if someone like Runoa was hanging around all the time, it would attract attention Demeter's peaceful familia could be ill-equipped to handle.