Melissa Rivers describes Joan's last moments: "I held her"

Melissa Rivers and Joan Rivers attend the 2014 NBCUniversal Cable Entertainment Upfronts at The Jacob K. Javits Convention Center on May 15, 2014, in New York.

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ET's Nancy O'Dell visited Melissa Rivers at her home, and the two shared tears over the memory of Joan Rivers eight months after her passing.

The mother-daughter bond between Joan and Melissa was unbreakable, and became a source of strength for Melissa in making the decision to take her mother off life support.

"No matter how prepared you are for it, you're not ready," Melissa told Nancy. "You're not ready, and they put the pen in your hand and they hand you the paper and you do what you have to do and what you were raised to do."

Joan remained strong for her family until the very end.

"They put a cot in the room for me, and I actually slept next to her bed that last night," Melissa said. "And then once they removed the ventilator, we knew it would take some time, and I got into the bed with her and held her. We were all there and standing there and I'm holding her and we're chatting, waiting. Finally the doctor says, 'Honestly, you guys need to leave the room for a while, because often people won't allow themselves to start to let go if everyone is in the room.' So we all took a little break for a second and about an hour after that she passed."

The special bond between Melissa and Joan carried over to Melissa's 14-year-old son Cooper, who mourned by his grandmother's bedside.

"[Cooper] sat there and held her hand and had a good cry," Melissa recalled. "He took his baseball hat and he put it in her hands and he said, 'Please make sure this stays with her.' And I made sure that it never left her side."

Joan's death followed a routine endoscopy in August to evaluate changes in her voice and to deal with acid reflux. She was placed in a medically induced coma after going into cardiac arrest and passed away a week later at the age of 81. The death was classified as a "therapeutic complication," which means that the death officially resulted from a predictable complication of medical therapy.

An inquiry allegedly revealed that a photo was taken in the procedure room -- a notion that makes Melissa physically ill.

"I think the day I found out, I actually threw up," Melissa said. "God! It's so wrong on so many levels, and it actually strikes fear in me that somehow, someday, somewhere, that will get out."

While Melissa still has bad days (she says in her darkest moments she "can't get off the floor") her new book, "The Book of Joan: Tales of Mirth, Mischief and Manipulation," comes with a lighthearted tone more reminiscent of how the comedienne lived her life.

"In our family we always believed that laughter was the best medicine," Melissa says. "Not only are there less side effects than Prozac but it's a lot cheaper than therapy. I wanted to write a book that would make my mother laugh. I hope it makes you laugh, too."

"The Book of Joan" is available now.