The handbag designer — born Katherine Brosnahan, but who changed her name after marrying Andy Spade — was found dead in her Manhattan apartment on June 5 in what was ruled a suicide.
The undated black and white photo posted by Brosnahan harkened to a happier time, with Spade eyeing a candle-laden cake during a birthday dinner as other celebrants flank her and appear to applaud. There is a big smile visible on the fashion icon's face.
“Happy Birthday Katy B. We miss you like heck,” Brosnahan wrote in the caption.
It's been a bittersweet year for the 28-year-old Brosnahan, who picked up her first Golden Globe win for her starring turn on Amazon's "The Marvelous Mrs. Maisel," but who lost both Spade and her paternal grandfather within a few weeks of each other in June.
Spade had been the first in the family to ascend to fame, opening her first handbag company in 1993, and quickly rising to be a fashion mainstay in New York City. Her sister revealed that the designer had struggled with mental illness for years, a claim echoed by her husband.
A day after her aunt's death, Brosnahan posted an Instagram video of Spade dancing with her husband in what she called the way "she would want to be remembered."
Brosnahan also honored her aunt a few days before the Instagram post in a more subtle manner. She was seen attending a New York Knicks game at Madison Square Garden last week with her husband, Jason Ralph, sporting a tan bag by Frances Valentine, the new label launched by Spade in 2016.