In the modern Gilded Age of New York, where Instagram is awash in unrestrained displays of wealth, Brandon and Candice Miller were royalty.

At their 10th wedding anniversary “Midsummer Night’s Dream” party, they celebrated with a few dozen friends in the backyard of their 5,500-square-foot vacation home in the Hamptons.

Beautiful women in gowns watched with their handsome husbands as the couple renewed their vows near a swimming pool strewn with peonies and rose petals beneath a canopy of lights.

It was a grand public display of their perfect life and marriage. Ms. Miller told a lifestyle blogger who wrote about the party that her husband’s speech “made me cry by the end with his authentic, raw emotion and romantic words.”

It all culminated in the kind of envy-inducing images anticipated by the roughly 80,000 followers of “Mama and Tata,” Ms. Miller’s popular Instagram feed, which featured a near-constant stream of photographs and videos of her glittering life.

The Midsummer Night party was in 2019. Five years later, the glamorous image that Ms. Miller cultivated and promoted has disappeared, replaced with heartbreak, anger and a mountain of once-secret debt.