What Friends Are For (1970)

A queer woman, dating a cis man for the first time, finds out she has a taboo medical disorder, vaginismus. She enlists the help of her lesbian best friend to attempt the at-home care method of vaginal dilators. Together they break down the concept of being able to have "regular" sex, while realizing despite their years of sapphic sexual encounters, they know shockingly little about the inner-workings of vaginas.