Mariah Carey went all the way in on her older sister Allison in her autobiography The Meaning Of Mariah Carey.

"Through all the years, both my sister and my brother have put me on the chopping block, sold lies to any gossip or rag or trashy website that would buy or listen. They have attacked me for decades. But when I was twelve years old, my sister drugged me with Valium, offered me a pinky nail full of cocaine, inflicted me with third-degree burns, and tried to sell me out to a pimp."

Now Allison is suing Mariah $1.25 million for emotional distress.  She claims Carey's allegations -- which she says she has no evidence of -- are particularly painful because she suffered a traumatic brain injury in 2015 and because Alison says their mother sexually abused her in satanic rituals. 

Allison has had a tough life, that for sure.  She was arrested in 2016, at age 55, for soliciting money in exchange for sexual favors from an undercover officer.  At the time, she said she was HIV positive.