Whoa. This is beyond catty.
Yesterday Sinead O'Connor published an open letter to Miley Cyrus, loaded with her concerns that the young singer was being pimped and exploited by her team.
And Miley responded by comparing her to Amanda Bynes — a person whose troubles have lead her into psychiatric treatment.
Miley tweeted a screengrab of what appears to have been a Sinead-written Twitter rant from the past, where she speaks of her own mental health concerns: