Unhinged (1982) by Don Gronquist

On their merry way to an outdoor festival, the three girls Terry, Nancy and Gloria get stuck in the middle of nowhere during a heavy rain and thunderstorm. Waking up after the shock of the accident, they find themselves (oh surprise!) not in their car, but disconnected of the world in a huge country house ruled by a severe Mrs Penrose and her daughter Marion, who caringly adopt them just as their own family members. And of course, they are very well locked after…

seen at: pickledfeet private videothek