WHITNEY HOUSTON’s mother Cissy has begged her niece, R&B legend Dionne Warwick, to mentor Whitney’s wild-child daughter, sources say.

But at 72, the “Walk On By” singer says that she’s too old to deal with headstrong 20-year-old Bobbi Kristina, who’s known as “Krissi,” the sources add.

“Cissy is really leaning on Dionne to take charge of Krissi,” said a family friend. “Dionne has been hesitant, but Cissy is trying to guilt her into stepping in.”

AS THE ENQUIRER HAS REPORTED, Cissy and Krissi have been engaged in a nasty feud over Whitney’s estate and legacy, with Krissi publicly slamming her grandmother’s memoir, “Remembering Whitney.”

Cissy, 79, is also concerned about Krissi’s engagement to Nick Gordon, who was unofficially adopted by Whitney and has lived with Krissi since she was 9, sources say.

Meanwhile, Dionne has called her late cousin Whitney “the little girl I never had,” and was one of the last people to speak to “The Bodyguard” singer before her tragic death in February 2012.

Dionne has also been close to Krissi over the years, and in a recent interview she expressed concern for the troubled teen.

“Bobbi is just like Whitney – she’s stubborn and won’t let anyone help her,” Dionne said. “She’s resentful that her mother was taken from her. She doesn’t feel close to anyone in her family anymore. She’s lost.”

That’s why Cissy is determined to enlist Dionne’s help, said the source.

“She will always love Krissi and be there for her to talk to, but keeping Krissi on track from day to day is a battle that Dionne just isn’t willing to take on.”