Lisa Rinna Learns on 'RHOBH' She Accidentally Taught Her Daughter Oral Sex
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The "Real Housewives of Beverly Hills" star says "if you're gonna learn it, you better learn it right."

On Tuesday's "Real Housewives of Beverly Hills," Lisa Rinna jetted to Tokyo to watch her daughters Delilah and Amelia take over the modeling world -- but things took an interesting turn when Delilah revealed to Rinna that she learned "how to give head" from her mother's "sex book."

Rinna brought Erika Girardi along to be "the teenage model wrangler" of the trip, but not even she was prepared for that kind of revelation.

While at dinner, Delilah and Amelia told Rinna and Erika about a video that had gone viral of a girl who regularly films herself overindulging on food.

"Don't you watch porn instead of people eating?" a perplexed Erika asked.

"Maybe I don't want to know about that yet," Rinna said laughing.

Then Delilah blurted out, "I'm not gonna lie, but your sex book taught me how to -- I was like 12 when I saw this -- it literally teaches you how to give head."

Lisa was stunned but managed to reply, "Well, if you're gonna learn it, you better learn it right."

"I never thought in a million years that my own children would read the book," she later told Bravo cams, holding up a copy of "Rinnavation: Getting Your Best Life Ever." Rinna then proceeded to read lines from the chapter in question but could not keep from laughing. "How could I have put this in a book?"

"The Real Housewives of Beverly Hills" airs Tuesday nights on Bravo.

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