Clare had never spent so much time on her own appearance. She'd paid for her hair to be styled, and bought new makeup. What made the night a particularly big deal for Clare is that she was a homeschool student.
Because she was a homeschool student, she didn't get the chance to mix with all the other students very much. This was a rare - and final chance - to see all the people she knew at school in the same place at the same time.