Joan Rivers was never one to keep her opinions to herself, about anything or anyone—or what they were wearing.

And that wasn't just for show. The pioneering comedienne, known for her incomparable work ethic and big heart as much as for the well-polished barbs that were her stock in trade, was as effusive with her feelings off-stage as on, the invitation to talk open-ended.

All of which has provided great solace for Melissa Rivers in the years since her mother's sudden death in September 2014 after suffering complications during a medical procedure. Even at 81, Joan had never slowed down long enough for fans to consider her mortality, let alone ponder an entertainment landscape without her untamable perspective.

"What saved me and got me through the last eight years was, nothing was left unsaid," Melissa told E! News' Francesca Amiker in an exclusive Zoom interview ahead of what would have been Joan's 90th birthday on June 8. ("She would not have been happy," her daughter deadpanned of the milestone.) "I'm so lucky that I knew she loved me. And she knew that I knew—and she knew I loved her."

Amid the countless memories she could single out, knowing they'd said it all has been the "overarching" remembrance for her, she shared, laughing heartily as she added, "And there were plenty of times in our relationship there was a lot to deal with."

The mom to 22-year-old son Cooper Endicott quipped that she dubbed her own household "Camp Run Amok" years ago, but the through line since her own childhood has been a family-first approach to parenting. Her mother and father Edgar Rosenberg, who died in 1987, provided "a clear definition of work life and home life," Melissa said, "or as I like to call it the separation of church and state."

And even though they were such famous personalities, she added, "who we were on TV or in the public eye was vastly different, and is still vastly different, than who we are in what I call our real lives."

But chatting all the time about everything was their norm—if her mom was here, she said, they'd be bingeing Succession and The Great and Joan would still be "giving Amal a run for George's heart" and fangirling over Ryans Gosling and Reynolds—and Melissa is thankful that what turned out to be their final talk was so routine.

"It was such a mother-daughter conversation," she recalled of the late-night phone call that, too tired to have a big discussion, she considered not picking up. And as "horrible" as the ensuing week was once Joan was hospitalized, "I am so fortunate for that moment where I can look back and say we had a completely normal—touched on work, touched on Cooper, touched on gossip—conversation. Typical, the trifecta."

Losing and subsequently mourning her mother, however, was what anyone who's been through a similar experience might recognize.

"Everyone expects celebrity grief to be different," Melissa observed. "And it's not. That's something I learned. Maybe there's more of an invasion of privacy, but that doesn't make the emotions any different for anyone, ever." 

She and Cooper traditionally mark Joan's birthday by lighting a candle and going out for a meal—during which, Melissa cracked, "I can literally feel her spirit slapping dessert out of my hands, saying, 'It's bathing suit season!' Bread would levitate off the table and be moved across the restaurant."

Whether that's inspired by real events or not, the 55-year-old's delivery can't help but remind you of someone.

In addition to their close personal bond, they were frequent creative collaborators, joining forces for everything from E!'s red carpet coverage and Fashion Police to their We tv series, Joan & Melissa: Joan Knows Best?, which ran for four seasons.

"We couldn't have done what we did [on E!] without each other," Melissa said. "It was a very special lightning-in-a-bottle thing." And on their reality show, "I think people really saw how much we could read each other. I could set her up and then she could knock it out of the park."

And yet Melissa didn't consider following in her mother's footsteps when it came to a career in comedy.

"No one in their right mind would ever try and live up to her," explained the author and host of Melissa Rivers' Group Text Podcast. "Everyone's like, 'Don't you want to do stand-up? You're so funny.' I'm like, 'No!' I wouldn't want to put myself in that situation."

Even without trying to go down that road, "there's enough comparisons," Melissa continued. And it bothered her mother that "I never got credit. She got all the credit and I rarely got any, and that was very frustrating to her, because we were such a team." 

Though she would argue that her mom's legacy has been self-sustaining—"She pretty much has taken care of keeping her legacy alive on her own, being such a legend"—the devoted daughter is making sure that Joan's vast body of work remains accessible for future generations: The Rivers archive, including Joan's famous one-bit-per-card catalog of jokes and all of her Tonight Show monologues, is headed to the National Comedy Center in Jamestown, N.Y.

Joan was headlining the Lucille Ball Comedy Festival (the I Love Lucy star was born in Jamestown) in 2011 when the creation of the multimedia center honoring the most important contributors to the comedic arts was announced, and Melissa was there for the groundbreaking in 2015. And now, timed to her mom's 90th, she will be delivering that treasure trove of, yes, hilarity, but also the evidence of the exacting effort that went into Joan's six-decade career.

"It's so exciting," Melissa said, and the eventual exhibit, due to open in 2025, is "really going to be a true salute to her life." Multiple places inquired about her mother's papers, she noted, but "this, for me, felt like the right home" alongside the works of George Carlin, Carl Reiner and so many more icons.

"Joan was one of the funniest people I ever met, and a friend for decades," fellow trailblazer Carol Burnett said about the museum's latest acquisition. "It's wonderful to know that her archives will join the National Comedy Center, a one-of-a-kind museum dreamed up by none other than Lucille Ball: a woman whom Joan and I both loved and admired very much."

Comedian Lewis Black, founding chair of the center's advisory board, called Joan's body of work "an essential part of comedy history and her full life was a model of creative resilience."

While fans wait for the in-person experience, they can pre-order Joan Rivers—The Diva Rides Again, a new four-disc box set of never-before-released comedy recordings and a 16-page collector's book, being released Aug. 18.

And though to every generation its comedic voices, Melissa feels that Joan would have kept rolling with the punchlines to this day, her as-long-as-they're-laughing approach to entertainment having proved pretty timeless. 

"I think she would have appreciated the conversations" about the state of comedy and whether some topics have become taboo, Melissa mused, but eventually her reliably brazen mother would have just sighed, rolled her eyes and cracked some more jokes.

"She always said, 'Making someone laugh is like giving them a mini-vacation,'" recalled the person who was closer to Joan than anybody. "Everyone needs to take a deep breath and remember it's okay to laugh. But I think at this point, she would just be like, 'Oh god, everybody, just...' I can't say it."

But if she did, Melissa added, "it wouldn't be the first time one of us had said 'f--k' on E!"