I don't much like Rowan in any of the books - to me she's another subversion of fictional archetypes and of the people Nick worships (or dislikes, sometimes unfairly). So you have Karen = head girl but also a bit wet and ineffectual, Ann = good but also deeply annoying, Rowan = games captain material but also prone to being deeply insensitive, a bit of a bully and who ends up making a disastrous decision vis a vis her own life, jacking it all in to run Trennels, and not very happily.