Didn't she state that one of her most popular songs is about using ecstasy? And isn't that illegal? As far as the advice to build a club and party at home, it would keep him off the street, but maybe "Stop acting like a spoiled, out of control brat" is better advice.Using
ecstasy is illegal, but as far as I know, there's no law against singing
about illegal activities.
Unless there's evidence of her actually using drugs herself or committing other crimes, rather than just singing about them, then I don't see any hypocrisy in her statement that "I'm doing a lot of [bleep], but I'm not doing anything illegal" or in suggesting that Bieber should do the same. Bieber doesn't seem to be listening to any normal, law-abiding adults about his behavior, so maybe another wild young celebrity pointing this out is exactly what he needs.
Also, this was not clear from the text, but Leno
was the one who asked if she had advice for Bieber in the video. This wasn't an unprompted statement from Cyrus, as if she thought she was some great authority on behavior. It was an answer to a direct question.