Three days after his death, Bethenny Frankel attended her on-off boyfriend Dennis Shields‘ funeral.

On Monday, the Real Housewives of New York City star was spotted arriving at the service on Long Island, New York.

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Shields was found dead of a suspected overdose in his Trump Tower apartment on Friday. He was 51.

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Frankel, 47, first met the New York City-based banker almost 30 years ago when he dated (and later married) one of her high school friends, Jill. Though she didn’t stay in touch with her classmate, Frankel and Shields shared other mutual pals and began dating in 2016, several months after he separated from his wife.

Jill addressed Shields’ death in an exclusive statement to PEOPLE on Friday.

“We are all heartbroken. Dennis was, and will always be, the love of my life. His spirit lives on in our children. Please respect our family’s privacy at this time,” she said.

Image zoom Dennis Shields and Bethenny Frankel Alessio Botticelli/GC

Frankel had always been candid about the complexities of their relationship, admitting that it wasn’t easy to define.

“I’ve been with someone on and off for years,” she said during an interview in May. “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.’ ”

Last week, a source told PEOPLE that the coupling was “unconventional and not always exclusive.”

“Bethenny loved him a great deal, but it was an unusual relationship,” said the source. “They would be together and then not. Sometimes these traditional relationships aren’t the best thing for everybody.”

The source added that Shields was a “steadying rock” for Frankel.

“He was very mild-mannered and she is like a force of nature,” the source said. “But she needed that in him.”

RELATED VIDEO: Bethenny Frankel Says She ‘Never Knows Exactly’ Where Relationship Stands with Dennis Shields

A source previously told PEOPLE that Shields was an important part of Frankel’s daughter Bryn’s life, too. (She shares the 8-year-old with ex-husband Jason Hoppy.)

“Bethenny and her daughter Bryn love Dennis and his family,” the source said. “They have been a support system during her negative divorce and a positive influence in Bryn’s life.”