Deadly Obsession? Bombshell Lawsuit Claims Nick Gordon Secretly Lusted For Bobbi Kristina Brown's 'Pretty Little White Girl' Friend

RadarOnline.com has learned that a third person was present when Nick Gordon allegedly battered Bobbi Kristina Brown during a life-ending fight on Jan. 31.

RadarOnline.com can reveal that the shocking allegation is included in an amended civil lawsuit filed against Gordon by Brown's conservator about what her troubled ex may still be trying to keep from cops.

The suit claims a "white girl" was lying on the bed in the couple's master suite as the alleged altercation unfolded in Brown's squalid townhouse in Roswell, Ga.

According to the suit, Gordon came out of the master bathroom and "got in bed, and laid his head on a female guest's ankle and stated, 'Now I want a pretty little white girl like you.'"

While the filing does not identify the female guest, she's believed to be 18-year-old Danyela Bradley, who has been named by RadarOnline.com as a blockbuster witness in the case.

In a shocking interview last March, Danyela's mother, Marlene, revealed that her daughter and Bradley's boyfriend, Max Lomas, were in the townhouse that tragic night.

Lomas called 911 after Brown was found unresponsive in a water-filled bathtub.

According to Marlene, Bradley said Gordon "did something to Bobbi Kristina."

In the suit it's alleged Gordon fought with Brown, calling her a "whore" and accusing her of cheating on him before giving her a "toxic cocktail rendering her unconscious."

Gordon then "put her face down in a tub of cold water causing her to suffer brain damage," the suit charged.