Sheryl Sandberg has credited Mark Zuckerberg with saving her life after the sudden death of her husband, saying the Facebook co-founder and his wife, Priscilla, were “why I’m walking”.

In an interview with the Guardian, Facebook’s chief operating officer spoke candidly about dealing with the loss of her husband, Dave Goldberg, who died of a heart attack in 2015 when they were in Mexico for the weekend.

“Mark is why I’m walking,” she said. “Most of what [he and Priscilla] did is not even in the book, because they did so much. When I felt so overwhelmed and so isolated and just needed to cry, I would grab him into his conference room and he would just sit there with me and be like, ‘We’re going to get through this and we want to get through it with you’. He did it over and over.”

Sandberg’s latest book, Option B, written with psychologist Adam Grant, explores her grief at the loss of Goldberg and acts as a manual for how to build resilience and achieve “post-traumatic growth”.

She wrote the book after posting a highly personal account of her first month as a widow on Facebook. The post attracted a huge outpouring of support and more than 74,000 comments to date. “After that, I didn’t feel so alone,” she said.

Sandberg described how her self-confidence had been shattered after the death of her husband, and that she had needed building up by colleagues including Zuckerberg. She described panicking to him about getting something wrong, and feeling better when he replied: “Really? I thought you made a good point in that meeting and helped us make a better decision.”

The executive, who started dating her old friend and tech billionaire Bobby Kotick 10 months after the death of her husband, also spoke about her anger towards people who judge widows who date again.

One Facebook user called her a “garbage whore”, while another said she was “one classy lady” for “already sharing fluids with a nice guy”. “I’m hoping that this book helps people stop judging people who date [after the loss of a partner], particularly women, because women get judged more harshly,” she said. “Men date sooner, men date more, and women get judged more. And, you know, obviously that’s super unfair.”

She added: “I think I’m helping people remember that dating, for those that want to do it, is part of moving forward, and it’s option B. If I could, I would only date Dave. I made that choice. I just had it taken away from me.”

In the book – for which she studied the research of behavioural scientists, neurologists and psychologists for tips on how to build resilience – Sandberg offers practical methods for dealing with grief. These include writing down three joyful experiences and three things done well every day.

The author of Lean-In admitted becoming more distanced from friends after the loss of her partner. Asked if she had been let down by loved ones, she replied: “I don’t know anyone who’s been through this who hasn’t had friends who disappointed them. I think we all go through that.”

But the process of dealing with the loss of her husband and best friend had given her life a deeper meaning, and more perspective on life’s difficulties, she said. “I would definitely choose to be before, so I could get Dave back. I’d give up all the growth. But the deeper sense of meaning, gratitude, purpose – those things are wonderful things.”

Read the full interview and an exclusive extract from Option B in Weekend magazine