Magic or Madness by Justine Larbalestier (2005)

Compelling young adult novel about a young girl in Sydney on the run with her mother. When her mother is committed and she goes to live with her grandmother, she learns some truths about her family, her life, and the reality of magic. Split between Sydney and NYC, it’s filled with Aussie slang (glossary included!) and a refreshingly diverse cast of characters. Followed by two sequels: Magic Lessons and Magic’s Child.