In Lost Voices, by Sarah Porter, orphan Luce lives with uncle Peter, a drunk in Alaska. When he attacks her, she becomes a myth: she transforms into a mermaid after he leaves.
When she is found by the queen of a tribe, she is exposed to the traditions of a mermaid: obey the rules and sink human boats using their siren voices, to gain revenge for the abuse each mermaid experienced. But Luce loves a few humans, like her missing and probably dead father. Will Luce surrender to peer pressure of the mermaids and commit mass murder?
I'd recommend the start of the Lost Voices series to teens who love to read about mermaids or sirens. Library's SWAN Online Catalog