Kristen Foster said she passed away on Sunday surrounded by her family and was “finally at peace in the arms of God”.
Brown was discovered face down and unresponsive in a bathtub on 31 January and placed in a medically induced coma. She never regained consciousness.
She was moved to a hospice in the city of Duluth, Georgia, a month ago after her condition deteriorated.
Brown was the only daughter of Houston and R&B singer Bobby Brown.
Houston was found dead in a hotel bath in Los Angeles in 2012.
The family posted a photo of Houston with Bobbi Kristina as a baby on whitneyhouston.com with the following message:
“It is hard to say goodbye. On Sunday, July 26, Bobbi Kristina Brown made her transition peacefully. The family thanks everyone for their loving thoughts and prayers. As Bobbi Kristina would say: ‘The wind is behind me and the sun is in my face.'”
“Bobbi Kristina Brown passed away July 26 2015, surrounded by her family,” Ms Foster added.
“She is finally at peace in the arms of God. We want to again thank everyone for their tremendous amount of love and support during these last few months.”
Singer Dionne Warwick, Whitney Houston’s cousin, described Bobbi Kristina as “a sweetheart”.
“She will be missed, that’s for sure. She was a good girl. She was a good little girl. She really was,” she told Bravo’s Watch What Happens Live.
Other stars paid tribute on Twitter, including Selma director Ava DuVernay, who said: “She seemed to be caught in the web of celebrity upon arrival. Twenty two years. A sad end. May the sister have peace now.”
The BBC’s Regan Morris in Los Angeles says Brown had dreamed of carrying on her mother’s legacy as a singer and actress, and had a few small TV roles – but her career had not yet taken off.
The day before she was found in the bathtub, Brown had tweeted: “Let’s start this career up&&moving OUT to TO YOU ALLLL quick shall we !?!???!”
She began performing with her mother as early as 1999, singing duets of My Love is Your Love and recording Little Drummer Boy for a holiday album in 2003.
She was taken to hospital twice with anxiety after her mother’s death.
In January, police said Brown was found in a bathtub in the suburban Atlanta home she shared with Nick Gordon, the man she called her husband. A police report described the incident as a “drowning”.
Mr Gordon said at the time she did not appear to be breathing and lacked a pulse before emergency services arrived. Although she was found face down in her bath, the 22-year-old also had bruises on the front of her body.
Authorities later concluded that she had suffered injuries to her face and mouth in a car crash several days earlier, saying they were not the result of foul play.
Brown was placed in a medically-induced coma and had been breathing with the aid of a ventilator before she died on Sunday.
Medical examiners have since said a post-mortem will be needed to evaluate what led to her death.
Fulton County Medical Examiner’s Office said the time that had elapsed from when she was found in January will “complicate” its effort to reconstruct events.
“Interpretation of autopsy findings and other information will also be challenging,” it said in a statement. “However, an autopsy could be helpful to address questions which may arise about the cause of her unresponsiveness and eventual death.”
Frosty relations between Mr Gordon and Brown’s relatives came to a head in June, when her court-appointed representative sued Gordon, accusing him of misrepresenting his relationship with her.
He was alleged to have transferred $11,000 (£7,091) of Brown’s funds into an account controlled solely by him while she was in hospital but was never charged.
As her health deteriorated last month, US authorities said they would be reviewing the circumstances of her condition “with greater interest”.
“An announcement regarding a charging decision, if any, will be made at the appropriate time,” Fulton County District Attorney Paul L Howard Jr told People magazine.
