'Ethel' documentary for HBO is Ethel Kennedy's first interview in 25 years

In the trailer for HBO's documentary "Ethel," Rory Kennedy prompts her mother, "And then we lost Daddy." After a long pause, Ethel Kennedy's face folds into a frown. "Let's tlk about something else," she says quietly.

The five-day interview between Emmy-winning filmmaker Rory and her mother is Ethel's first interview in 25 years. She and Rory attended the Television Critics Association Press Tour on Wednesday to discuss the film with critics, and Rory admitted that HBO's Sheila Nevins had to really push her to do the film.

"I didn't really want to do it mostly for personal reasons. I didn't want to ask my mother and my siblings to go through some of the difficult moments that have been part of our history," Rory says. She was shocked that Ethel agreed to do it, and said she couldn't turn it down then.

"It said a lot that she was willing to do it," Rory continues. "It was a real gift and I'm so grateful that I had that experience."

The film highlights the key differences between Ethel's upbringing in the Skakel family and the Kennedy routing. "The Kennedys were very organized. Dinner was always served at 7:15 and if you were a minute late it really wasn't worth it," Ethel joked with critics. "In my family you never knew when dinner was going to be. It could be at 7 or it could be at 10."

Things grew more serious when she was asked about her ability to be strong throughout their darker moments. "There was nothing really quiet about our family. It was a little helter-skelter, and 'Look out, here those brothers come again,'" she says. "It's embarrassing, or uncomfortable to talk about, but I'd say faith had a lot to do with being able to get through everything. It was always very comforting. When we lost Bobby, I would wake up in the morning and think, 'Oh, he's okay, he's in Heaven, and he's with Jack and a lot of my brothers and sisters and my parents. It made it very easy to get through the day thinking he was okay."

When asked what the best part of making the emotional film was, Rory says frankly, "Being done with it."

"And being together," adds Ethel. When asked what she got out of the process, she turns to her daughter. "How amazingly brilliant and fun to be with you are," she says. "She is really the best."

The film will premiere on HBO on Oct. 18.