There's trouble brewing between Miley Cyrus and Sinead O'Connor.

Cyrus basically called O'Connor crazy on Thursday and compared her to Amanda Bynes (who is in a rehab facility after undergoing psychiatric care for several weeks).

Cyrus' response comes after O'Connor wrote her an open letter, urging her to stop being naked and licking sledgehammers.

No, really ... O'Connor did.

According to TooFab.com, O'Connor posted the letter on her blog, warning Cyrus about being "prostituted" in the music business.

So why is O'Connor suddenly turning all mothering-mentor on Cyrus? Could have something to do with Cyrus telling Rolling Stone that her "Wrecking Ball" video is a "modern" version of O'Connor's "Nothing Compares 2 U" video.

"I wanted it to be tough but really pretty," she told the magazine. "That's what Sinead did with her hair and everything."

Uh ... right. O'Connor isn't buying it.

"I am extremely concerned for you that those around you have led you to believe, or encouraged you in your own belief, that it is in any way 'cool' to be naked and licking sledgehammers in your videos," she wrote. "You also said in Rolling Stone that your look is based on mine. The look I chose, I chose on purpose at a time when my record company was encouraging me to do what you have done," she says. "I felt I would rather be judged on my talent and not my looks. I am happy that I made that choice."

Sounds rational.

She wrote on: "The music business doesn't give a (expletive) about you, or any of us. They will prostitute you for all you are worth, and cleverly make you think it's what YOU wanted," she wrote. "And when you end up in rehab as a result of being prostituted, 'they' will be sunning themselves on their yachts in Antigua, which they bought by selling your body and you will find yourself very alone."

Yet, she also praised Cyrus, which was pretty nice. Maybe that's why Cyrus thinks she's crazy.

"As for the shedding of the Hannah Montana image, whoever is telling you getting naked is the way to do that does absolutely NOT respect your talent, or you as a young lady," she wrote. "Your records are good enough for you not to need any shedding of Hannah Montana. She's waaaaaaay gone by now. Not because you got naked but because you make great records."

The website reported that Cyrus responded on Twitter. "Before Amanda Bynes.... There was...." Cyrus posted, with a photo of O'Connor's tweets, in which she mentions "urgently" needing a psychiatrist to get her "back on meds."

Your play, Sinead.

Contact Tony Hicks at Facebook.com/BayAreaNewsGroup.TonyHicks or Twitter.com/insertfoot.


In this Saturday, Sept. 21, 2013 file photo, Miley Cyrus performs at IHeartRadio Music Festival, day 2, in Las Vegas, NV.
In this Saturday, Sept. 21, 2013 file photo, Miley Cyrus performs at IHeartRadio Music Festival, day 2, in Las Vegas, NV. (Photo by Al Powers/Powers Imagery/Invision /AP, File)