According to the suit ... Mariah's book alleges Alison "gave her Valium, tried to pimp her out and threw a cup of boiling hot tea on her causing third-degree burns" when Mariah was 12. Alison disputes these allegations and claims Mariah hasn't provided any evidence to support them.
Alison goes on to accuse Mariah of making these outrageous claims despite knowing Alison suffers from trauma herself from the alleged abuse she suffered as a child at the hands of their mother.
Alison claims their mother subjected her to satanic rituals and sexual activity at a young age ... allegations she previously made when she sued their mother for sexual abuse last year.
Mariah's estranged sister also says she suffered a traumatic brain injury during a 2015 home invasion, and suggests Mariah ignored her vulnerabilities and "used her status as a public figure to attack her penniless sister" to promote her book.
Alison's suing for infliction of emotional distress. We reached out to Mariah ... no word back so far.