Joely and Tricia -- who share the same father as Carrie, the late singer Eddie Fisher -- sat down for a new emotional interview, in which they talk about losing their "hero" and big sister.
"She spoke her mind and spoke her truth in this just bold way that made everyone feel a little bit more comfortable about their own flaws and, felt even more interesting for having flaws," Tricia tells Good Morning America
. "She was the coolest big sister in the world."
"I think that she was more sensitive," she adds about the Carrie that they knew aside from her public persona. "She was secretly soft, she was extremely generous. You would walk in and she would just hand you something in her room."
Joely reveals the heartbreaking last conversation she had with Carrie, which happened on the night before the Star Wars
actress suffered cardiac arrest
while on a flight from London to Los Angeles.
"It was sort of out of the blue -- we talked about age, because she was floored that she was turning 60, we talked about our children, we talked about our frail mothers and promised to see her for Christmas."
After learning of her medical emergency, the sisters rushed to the hospital, where they encountered a distraught Debbie Reynolds. Debbie died just one day after her daughter
at age 84, after suffering a stroke.
"She was praying for more time. She kept saying that she was ... she wanted more time," Joely says of Debbie. "And I knew that if Carrie wasn't going to survive this, that Debbie would not. You knew it. You could feel it in her tiny little beautiful body. You could see it in her face. She would not last without her on the planet. She wouldn't, and she didn't."
As for Carrie's daughter, 24-year-old actress Billie Lourd
, Joely and Tricia have nothing but praise for how she's been able to cope in the face of tragedy.
"Billie was handling everything. She's an amazing, amazing girl," Tricia says about Billie's demeanor in the hospital. "She was obviously, you know, rattled to her core -- it was her mom -- but she was handling it."
Billie broke her silence
since the death of her mother and grandmother on Monday, thanking fans for their support. "Receiving all of your prayers and kind words over the past week has given me strength during a time I thought strength could not exist," she Instagrammed alongside a childhood photo of herself with Carrie and Debbie. "There are no words to express how much I will miss my Abadaba and my one and only Momby. Your love and support means the world to me."
Watch the video below to see how Billie's Scream Queen
co-stars -- including Ariana Grande, Taylor Lautner and Lea Michele -- have rallied around her
since Carrie's death.