A year after WHITNEY HOUSTON’s tragic death, the singer’s lesbian lie has been exposed – and sources say it’s causing a major rift between her mom, CISSY HOUSTON, and Nippy’s childhood friend, ROBYN CRAWFORD.

In a new book docu­menting the life and death of her famous daughter, “Remembering Whitney: My Story of Love, Loss, and the Night the Mu­sic Stopped,” 79-year-old Cissy “absolutely trashes Robyn,” says a source.

But whole Cissy insists through­out the book she has no problem with Robyn’s sexuality – and claims that she doesn’t know the true nature of Whitney and Robyn’s relationship – other sources say she’s NOT telling the whole truth.

“Cissy has caught herself up in a shocking web of lies,” a close source revealed. “She claims she didn’t care whether Robyn was gay, but she hated Robyn for the rumors that she and Whitney were lovers. She was worried that the sto­ries would destroy her daughter’s career.”

Whitney – who drowned in a bathtub at the Beverly Hilton hotel on Feb. 11, 2012 – was just 16 when she and Robyn met while working as camp coun­selors in 1979. They hit it off instantly, and Whitney went on to name Robyn her “personal assis­tant” when her career started to take off in the late 1980s. The two women even lived together.

“I had a bad feeling about that child from the first time I saw her,” Cissy writes. “There was something about the way she carried herself, a kind of arrogance, that I didn’t like.”

The source notes that Cissy was so concerned about Whitney’s re­lationship with Robyn “she did everything in her power to stop it,” and even pushed Whitney to pur­sue a romance with hip-hop bad boy Bobby Brown to get her away from Robyn.

In his 1998 book “Good Girl Bad Girl,” co-au­thor Kevin Ammons – who dated Whitney’s former publicist Regina Brown – quotes Cissy as saying it wasn’t “natural” for the two women to be so close. He goes on to allege that Cissy exploded at Robyn for fighting with Whitney, who had just received a gift of 400 roses from Brown.

That story does NOT appear in Cissy’s book.

Whitney and Robyn drifted apart after the superstar singer married Brown in 1992, and throughout the years, both women denied they’d had a lesbian relationship.

But British gay rights activist Peter Tatchell offers his opinion that “perhaps her in­ability to express her same-sex love contributed to her substance abuse and decline.”

Meanwhile, Robyn is said to be livid over the book and con­cerned about her reputation.

“Robyn doesn’t want Cissy to have the final say,” the source explained. “Now, she may even write her own book to set history straight.”