The Avengers

you are a Hydra experiment that they called "The Porcelain Doll Project" they were trying to make someone just like a doll. good at everything and absolutely beautiful. you were supposed to be perfect but you failed to meet those standards so they used you as a soldier due to your fighting abilities. eventually you got out (you decide how) and you moved away and hid. when the Avengers were looking through an old Hydra base for more info on Hydra they found files about the Porcelain Project and eventually tracked you down.