Bobbi Kristina Brown's partner is accused of giving her a "toxic cocktail" and putting her face-down in water, in a lawsuit filed by the administrator of her estate.
The administrator has added a wrongful death count to the lawsuit against Nick Gordon.
Brown, the 22-year-old daughter of Whitney Houston, died in hospice care on July 26, six months after she was found face-down and unresponsive in a bathtub in her Atlanta, Georgia, home.
Mr Gordon has not been charged criminally.
An initial post-mortem found no obvious cause of death and the medical examiner's office said it would probably take several weeks to rule on a manner and cause of death.
The prosecutor's office has said they will review the investigative file.