The Bad Seed
(she burns him alive)
Kristine and Kenneth seem to have the perfect daughter, eight year old Rhoda (played by 11 year old Patty McCormack) however this jewelled sunglass wearing, rollerskating charmer is actually an amoral psychopath.
After a boy drowns at a school picnic and his drunken mother turns up at her house ranting, Kristine begins to suspect that Rhoda may have had something to do with the death.
It's slightly campy but is actually an extremely dark story of a serial killer. So dark that the film makers changed the original books ending and added a light hearted comedy scene during the credits.
Rhoda is an icy calculating shit but seems to have quite modern sensibilities, well maybe without the murders but she's materialistic and an expert at emotional manipulation.
YES - girl hasn't gone bad, girls born bad.