What is this book about a girl who discovers she is a battle robot?

A girl was a robot in disguise and her "mom" was her engineer. She was a battle robot and she would’ve killed millions if it wasn’t for her mom. Then they get found out, go on the run, her mom gets kidnapped and she has to fight with other better versions of her made by her "dad". She escapes and swears revenge because her mom is dead. This doesn’t do it justice

The way she finds out she’s a robot is that she goes on a date with a guy at a carnival and she trips and falls exposing her wires.