Book request: Heres what I can recall YA The cover was blue with a girls face on the frontThe girl began to suspect she was part mermaid, she has a single father who didn't care for her she makes friends with twins who have just moved in she ends up pushing them apart and seducing the male, as well as many other older males (very Lolita) she witnesses the town butcher commit suicide via drowning she has implied sex with the male twin in the female twins bed she eventually goes missing and you read her jumping into the sea but you dont find out if she is actually a mermaid the twins end up meeting again and the female twin mistakes her brothers wife for the original girl and nearly goes off on one the mermaid girl had long blonde hair and blue or green eyes. She was called Serena or Rainer or something like that.I read it around 2011-13

Matching book description:  is a merrymaid or so she believes . . . Ellen and Jack are evacuated from London to Cornwall during the Second World War. Ellen relishes the opportunity to better herself. Jack is different. He finds the attention from his new family stifling and seeks freedom in the arms of Selina, the mysterious local girl he sees at the shore. Selina, Ellen and Jack's li  is a merrymaid or so she believes . . . Ellen and Jack are evacuated from London to Cornwall during the Second World War. Ellen relishes the opportunity to better herself. Jack is different. He finds the attention from his new family stifling and seeks freedom in the arms of Selina, the mysterious local girl he sees at the shore. Selina, Ellen and Jack's lives are intertwined in a series of events that lead to tragedy. ...more