Cassie didn't always get the chance to make it to the island for festivals - and she didn't always go, because while in some ways the Amazons were partially her people, she also didn't quite fit in with them. She wasn't human and wasn't an Amazonian; she was a demigod, really, and they weren't really around for her to talk to. But rather than dwell on the differences, Cassie spent most of her time just focusing on the day to day stuff: school, friends, and being a Titan.
When Mia had told her she was heading out to the Island, Cassie had decided to join her for at least part of her trip, and at the moment she was glad she did. Festivals on Themyscira were downright fun, and it helped Cassie sometimes forget about regular stresses and just focus on celebrating. When the arm was suddenly slung across her shoulders, Cassie glanced over, then grinned at Mia and slipped her own arms around her friend's waist.