Weird black comedy from the 70s or 80s

I thought is had Madeline Kahn in it but maybe just an Actress of that generation and look... There is a scene where a mother is gas lighting her daughters fiancé. She walks in on him in the shower and he uses shaving cream to cover himself... only it's hair remover... Later she pays hospital orderlies to shave one of his legs and tell them he is a flasher with no pubic hair... It was strange but funny.