The two met as teenage summer camp counselors, a relationship that was based around the older Crawford, 19, looking out for Houston, 17.
"She said I don't believe we should be physical anymore", Crawford recalled.
"I kept it safe", Crawford added.
Explaining the nature of their relationship, Crawford writes, "We never talked about labels, like lesbian or gay".
"At the apartment, we took off our clothes, and for the first time, we touched each other", she writes.
Crawford writes that Houston instructed her she experimented with cocaine for the first time at age 14, and would normally convey to her, "Cocaine can not go in which we're heading", but always explained she "wasn't ready" when Crawford pushed her to stop or search for help.
In the People excerpts of her memoir, Crawford further details how and why the physical aspect of her relationship with Houston came to an end.
A preview of her Dateline sit-down aired Thursday on the Today show and Crawford talked about why she chose to write A Song for You: My Life with Whitney Houston, having kept silent about their love affair for decades.
When director Kevin MacDonald was developing his 2018 documentary about the singer, there were initial discussions with Crawford about participation in the production, but she eventually declined. Which is why Crawford wrote the book.
Whitney's family, including her mother Cissy Houston, did not approve of the relationship.
Robyn penned: 'She was more interested in Eddie Murphy [than Bobby Brown] but he was elusive'. The book comes out on November 12. But now, someone else is talking about falling in love with Whitney: her best friend, Robyn Crawford. Crawford said Houston is the one who broke it off, giving her a gift of a Bible along with the news.
"I have a lot of handsome, wonderful, exciting, adventurous, loving, caring memories of Whitney", she says.
She went on to describe Whitney's preparations for dinner one night with the Saturday Night Live comic, who was scheduled to visit her at her New Jersey mansion. As previously reported, Whitneydied in 2012 from accidental drowning.