Frankel has spent the last few days at her home in Bridgehampton.
She appeared to be unaware of the tragic news on Friday and was adding to her Instagram story until around noon.
She and Shields dated intermittently from 2016 on wards but always remained friends. He appeared occasionally on the Bravo show in which she stars.
The SkinnyGirl mogul has not commented on Shields' death.
Shields had four children with his estranged wife Jill. The pair were married for 26 years before separating in 2016, not long before he and Frankel became an item.
On Friday, Jill, an interior designer, told DailyMail.com she was 'devastated' by the news.
"We are all heartbroken. Dennis was and always will be the love of my life. His spirit lives on in our children." She added that he was a "loving father and friend."
The couple had four children together; daughters Tyler, 24, Darien, 20, and Kelsey, who is in college, and one son, Zachary, 23.
Shields was the CEO of LawCash, a Brooklyn-based firm which bankrolls lawsuits against New York City.
He was also the executive chairman of Esquire bank and the fin-tech start-up YieldStreet.
The businessman lived on the 42nd floor of the luxury building in a two bedroom apartment which he bought for $3million in 2012.
He put it on the market in April 2017 for $4.75million and it is still up for sale.
The first of Frankel's housewives to speak out on Friday was Sonja Morgan.
'This is heartbreaking. I spoke to Bethenny yesterday to say I was going to Coast Rica, in case she wanted to come and get away. She's been working so much," she told RadarOnline.
Carol Radziwill, who spent the last season fighting with her one-time best friend Bethenny, later tweeted: "I just heard the sad news about Dennis. He was a good man. My condolences to all his family and friends. So tragic."
Frankel and Shields had been friends for years before they began dating.
She called one of his daughters one of her Bravo show's infamous reunion episodes to prove their relationship was wholesome after it was claimed that they began seeing each other before his separation.
During that call, Shields' daughter spoke of the back surgery which was still causing him pain when he died.
In May, after parting ways, Frankel alluded to a reconciliation, telling Steve Harvey: 'I've been with someone on and off for years.
"It's like a partnership where if we're not being teammates and it's not working and one man is down, then the other man is down. We're trying to really kind of be good partners and be good teammates and I think relationships oddly are — and this sounds cold — but a little bit like business.
"If both people aren't happy about it but slightly uncomfortable and giving up something or giving in [to] something, it doesn't work. So both partners have to say, 'All right, I'm in it for this.' And I think we might be at that point, believe it or not. I haven't said that to anyone yet."
