Three Ripening Cherries (1979)

Three high school sisters with a cougar mom who sits them down for a frank discussion about sex. It's clear the young women are eager to enter this aspect of their adult lives so mamma decides to give them some blunt "dos and don'ts". Sitting around the kitchen table, mom dispenses some cautionary tales based on her own experiences. Seems she was once lured to the home of a trusted middle-aged man who drugged and seduced her. Mom explains that the experience was terrible and advises her daughters to save themselves for the right man. Fine up to now. However, she then almost gleefully recounts an abundance of other sexual experiences throughout her life, all of which were seemingly far more exciting and satisfying.