Cosette was a part of the Bane pack. She was very timid and shy; she stayed close to Sabine.
When the Nightshade pack went to Eden Cosette was there sitting with Sabine. Calla, being kind of stupid, sat down with Sabine who clearly disliked Calla. Cosette offered her a shy smile and said hello. When Sabine freaked out she calmy picked up her mess and sat there.