The Girl from Everywhere, by Heidi Heilig

Nix is a little bit pirate and a little bit time traveler, and a lot confused by her relationship with her father, her best friend and her future. She's been a passenger on her father's ship, the Temptation, for her whole life, as he's been seeking the perfect map that can bring them all back to a time before Nix's mother died. But if the past gets changed, what will happen to the present, and the future? Nix may not be the same person, or even exist at all. She's torn between trusting her father and trusting her instincts. Worse, she becomes embroiled in a political upheaval -- something she knows from the future takes place in the present where she is -- and she finds her loyalties and morals tested by the decisions she has to make.
This book is a very engaging mix of fantasy/sci-fi and historical fiction (much of the action takes place in Hawaii in the 1880s), with some mythology tossed in. The title is a little misleading (the story is much more about Nix's present and future than her origins) but she does need to decide if she wants to learn to Navigate herself and what that might mean. This book also has a lot of consideration of the impact of time travel, which can sometimes be hard to follow (like when Nix meets a crucial character whose own present depends on choices she might or might not make in the future). The adventure always keeps the book moving, however, and it ends very satisfyingly, wrapping up this story pretty neatly but also setting up for the sequel which is coming soon. Highly recommended!