When did Claire get in the clique?

Answer 1

Claire has always been a IN and Out for Massie, in the end of the first, she was both.

But she officialy became in the clique in the third book when Alicia quit.

When Alicia came back, Massie kept Claire IN.

Answer 2

Claire became part of the clique last summer when she started hanging out with the group more often and attending their gatherings and events.