The music icon is looking back at the life and legacy of Lena Horne, alongside her granddaughter.
"Lena Horne was one of my major mentors," Warwick told ET's Kevin Frazier during a recent interview via video chat. "I called her Mama, she called me daughter. She was one of the many mentors that I had, but she was one of the very special ones to me. Because of the way she treated me."
"The one thing I never forgot and never will forget, and have passed it on to my children and my grandchildren, is what she told me many, many years ago, and that was, 'Be who you be. You cannot be anyone other than that,'" the songstress recalled. "That's something I never forgot, and anybody that knows me knows that Dionne is always Dionne."
Horne -- who died in 2010 at the age of 92 -- was an acclaimed singer and celebrated actress. She earned four GRAMMY awards -- including a lifetime achievement award in 1989 -- as well as a Tony Award in 1981 for Lena Horne: The Lady and Her Music, among countless other accolades.
Apart from her many accomplishments in showbusiness -- which influenced countless artists who followed in her wake -- Horne was also a passionate civil rights activist and a dedicated proponent of the civil rights movement across the nation.
For Warwick, Horne was the kind of woman who exuded "regality" and had a magnetic and commanding presence, as if she was saying in her mind, "You're gonna look at me, but then going you're gonna look at me the way I want you to look at me. [Feel about me what] I want you to feel about me."
"It was her whole essence," Warwick added. "Just magic."
Horne was the first Black woman to ever be a contracted actor with a major Hollywood studio, MGM. However, she grew disillusioned with Hollywood after continuous incidents of discrimination and being cast in stereotypical, demeaning or offense roles. So, she stepped away from the front of the camera and took the stage to build up her career as a live performer and singer, where she found a new audience and new fame.
"She's a trailblazer. A pioneer," Warwick shared. "She gave me and everybody that looks like me something to look forward to.... it was a legacy that literally she passed on. She passed it on to me, she passed it on to every little Black girl that had any aspirations of doing anything at all."
Meanwhile, Lumet, Horne's granddaughter, is developing a series based on the stage and screen legend's life, and she's taking the weight and responsibility of the challenge to heart.
"My job is to document a woman discovering herself," Lumet said of the project. "Finding herself within this crazy whirlwind of America, of Blackness, of entertainment."
Looking at the challenges Horne faced and overcame, Lumet marveled at the grace and determination her grandmother exhibited.
"People didn't want to do her hair, people didn't want to do her makeup, people didn't want to dress her. There were issues about what entrances she was allowed to use," Lumet said, "and yet she had to be this exquisite performer and this exquisite beauty you saw in front of you."
While facing down these struggles, Horne managed to break barriers and open up possibilities for other performers as well.
"There are some people who just sort of, by the nature of their being, kind of lift all of us up and move us along," Lumet explained. "I think that she's quite miraculous."