Cissy Houston, 79, said that her life changed forever when she received a phone call telling her the singer had been found dead in the bathtub of her hotel room last February.
"That was the moment my life shattered," she said in her new book 'Remembering Whitney'.
"I don't know what I did or said after that. I was told later that I screamed so loudly that the while building must have heard me, but my mind was absolute blank, except for one thought - that my baby had gone.
"Even now, nearly a year later, I sometimes just ache, wishing I could hug my Nippy one last time. I never ever thought she would go before me.
"The first days after the news blurred into a terrible haze. I would fall into a fitful sleep and wake up and realise an hour or two later that my greatest nightmare was real."
However, Cissy admitted that although the rest of Whitney's family were overcome with emotion during the troubled singer's funeral, the New Jersey ceremony was the first time she felt at peace and was able to accept what had happened to her daughter.
"But then something happened that very unexpectedly made me feel better.
"When my daughter's body came home to New Jersey, that was the first time I felt and real comfort since I'd learned of her death. Strangely, the moment I saw my sweet daughter lying there in the casket, I felt at peace for the first time.
"She had such a serene look on her face, as is she were just sleeping. I reached out and touched her face, her arm, her hand… seeing her face so peaceful, so at rest, I was finally able to accept what happened.
"Seeing my daughter, even in death, gave me strength."
Exclusive extracts from 'Remembering Whitney' are being published in The Sun newspaper.