A family—a man and woman along with their two children—spends a summer vacation at a beach house, but the young woman they employ as a nanny turns out to be more attractive than anticipated and possesses malicious plans. "Summer Girl," made for television in 1983, shares similarities with films like "The Babysitter" (from 1980), which subsequently impacted later movies such as “Poison Ivy” (1992). I’d even say it …