70s bathtub scene

i saw this film in 1977. A very middle-class American woman is planning a dinner party and yelling at her Mexican maid. She then decides to take a bath. The phone rings and a rather long-winded female friend is on the line. The bathtub lady’s attention wanders and she starts to pleasure herself (really, this was not a porn film; I saw it on Danish TV). After she finishes, she realizes that her friend has hung up on her and she says:”How embarrassing!” I’ve been looking to finish watching this movie for nigh on forty years. Definitely American, in color.

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