I unfortunately don't have this book with me, so I can't say what two traits Jahnna used to "exemplify" the Capricorn. In this story, Cat moves back to her childhood home town after spending years apart. She has a phobia about houses with stairs - they live in a one-floor house - and her past visiting the therapists makes her reticent about having friends. To her surprise, she is invited to join an exclusive club in her high school (think sorority exclusiveness) and partakes in making a float for homecoming. Along the way she falls for a boy, an artist (forgot his name), but a sleepover at the club's president's house leads to some pretty traumatic events and her memories surfacing again.
Just like Mirror Image this book is probably better read lightly. It deals with loss somewhat realistically though I think it could have done more at the end, besides an instant happy ending.