Miley Cyrus-Sinead O'Connor feud escalates

Trey Barrineau | USA TODAY

Grab some popcorn.

The Miley Cyrus-Sinead O'Connor war of words reached DEFCON 2 on Thursday afternoon when the controversial Irish singer, 46, posted a second "open letter" to the controversial American singer, 19 -- then threatened legal action against the former Hannah Montana star.

O'Connor's latest posts were a response to this tweet from Cyrus, which links to a photo of O'Connor's Twitter timeline from two years ago, a period when O'Connor says she was "unwell and seeking help" for mental-health issues.

O'Connor responded to the tweet on her Facebook page. An excerpt:

Miley… Really? Who the f*&k is advising you? Because taking me on is even more f*&kin' stupid than behaving like a prostitute and calling it feminism. You have posted today tweets of mine which are two years old, which were posted by me when I was unwell and seeking help so as to make them look like they are recent. In doing so you mock myself and Amanda Bynes for having suffered with mental health issues and for having sought help.... Remove your tweets immediately or you will hear from my lawyers. I am certain you will be hearing from all manner of mental health advocacy groups also. It is not acceptable to mock any person for having suffered. It is most unbecoming of you to respond in such a fashion to someone who expressed care for you.

In another Facebook post soon after, O'Connor reiterates her threat of legal action: "Ms Cyrus' lawyers will be contacted by mine regarding this matter. I confirm also that I do not at all support or condone the abuse or mockery of those who have been brave enough to openly discuss mental health issues. Mockery causes deaths. Period. It is an unacceptable form of bullying, no matter who it is doing the bullying."

Just to keep the timeline straight, Cyrus' derogatory tweet was inspired by O'Connor's out-of-the-blue first open letter to her earlier on Thursday, in which the Nothing Compares 2 U singer urged the Wrecking Ball singer to stop "allowing yourself to be pimped, whether it's the music business or yourself doing the pimping."

Later on Thursday night, Cyrus responded via Twitter:

"Sinead. I don't have time to write you an open letter cause Im hosting & performing on SNL this week."

"So if youd like to meet up and talk lemme know in your next letter. :)"