70s/80s Euro (German?) 'Forced Lesbian' Themed Film

I saw this in the late 80's on some premium cable channel - I think it was hardcore or pretty close to it. The plot involves some kind of nanny or nurse, maybe schoolteacher coming to some house in the country inhabited by an older man, his younger brunette wife and some others/maids etc. -- The visiting woman has her hair up in a tight bun most of the time and wears glasses, is stern and aggressive. She quickly seduces one of the maids and the wife of the house walks in on her being orally serviced. After that, this woman really has it in for the wife, all over her whenever they're alone. She chases her down in a wooded area and hikes up her dress in this clip, whispering in German, I think. Eventually, the older husband catches on and invites his wife to share a bath with him - the lesbian walks in on them, strips and gets in and proceeds to lick the helpless wife all over while the husband gets off on it. -- I've been looking for this film for like 30 years, if anyone knows you'd be my total hero!!