"I spoke to Whitney the day that she passed," Warwick said today on " Good Morning America." "I spoke to her that morning. She said, 'You're here, aren't you? You're coming to the party, aren't you?' I said, 'Yeah, I'm going to be there' and she said, 'Thank you, I want you to be here. You've got to be here for me.'"
Houston was found dead Feb. 11 in the bathroom of her hotel room at the Beverly Hilton Hotel in Los Angeles where the 48-year-old singer was preparing to attend a pre-Grammy Awards party thrown each year by her mentor, the music mogul Clive Davis.
"I spoke to her that afternoon once I landed in L.A. and that was it," Warwick, 71, said of their last conversation. "She was so up and ready and happy. She had everything in the world to live for. She had a new film that was an absolute dream to make and do. She was getting ready to go back into the studio to record. She was getting her vocals together."
Houston had just completed filming the movie "Sparkle" with former "American Idol" contestant Jordin Sparks. The six-time Grammy winner was also working with Davis to release a new album.
"It's very, very surreal. It hasn't really sunk in yet," Warwick said of the death of Houston, whom she called "the little girl I never had." "I have not had an opportunity to really mourn or completely break down, which I will do, I know that."
Warwick spoke at the star-studded, nearly four-hour funeral ceremony held for Houston last month in Newark, N.J., where she was seen comforting her aunt and Houston's mom, Cissy.
"I am so proud of her. She's really holding up so very well," Warwick said of singer Cissy Houston. "She has her moments of course and will continue to have her moments. I think she's coming to terms with it just about now. It's going to take quite a bit of time."
Warwick has also been there to support Houston's only child, 19-year-old Bobbi Kristina, whom new reports say will inherit her mother's entire fortune. Houston's 19-page will reportedly leaves all her belongings, including money and jewelry, to Bobbi Kristina in a trust that will dole out money to her at ages 21, 25 and 30,
Bobbi Kristina, Houston's child with ex-husband, singer Bobby Brown, took the death particularly hard and was hospitalized twice for stress and anxiety after her mother died.
"She will have it [support], of course," Warwick said. "That's the one thing I love about my family. We are family. She has the support that she actually needs."