"I remember her laugh," Alan Cumming, who starred with the actress in Cabaret on Broadway, told PEOPLE. "She was really kind to me."
After the late actress' father, Tony Richardson, died of AIDS-related causes in 1991, she devoted herself to helping to fight HIV/AIDS. She joined AmfAR's board of trustess in 2006. In 1999, she was the driving force behind "Unforgettable: Fashion of the Oscars," an auction of Academy Award gowns that raised more than $1.5 million for AIDS research. Richardson died on March 18, 2009 after suffering a fatal brain injury during a skiing accident in Canada.
Those who knew Richardson recalled her as a gracious hostess and accomplished cook. "She made a wonderful Boeuf Bourguignon," said Stanley Tucci, who emceed the event at Cipriani 42nd Street in Manhattan. "You never had a bad meal at Natasha's house."
Julianna Margulies concurred: "If you slept over at her house, first thing in the morning [there was] fresh baked bread."
Donna Karan, who designed Richardson's wedding gown when she married Liam Neeson, said that the actress was "a woman full of joy and happiness."
During the ceremony, Richardson's mother, Vanessa Redgrave, gave a heartfelt tribute to her daughter. "My darling Natasha, I'm so proud of your courage, your hard work, your total commitment and your beautiful, life-giving spirit. Thank you," she said.
Lady Gaga sang at the event – and so did Oscar-winning actress Meryl Streep. "It really takes guts to get up and sing after Lady Gaga," Streep quipped before launching into "The Parting Glass," a traditional Irish Song.
As the song ended, Streep sang, "But as it falls unto my lot that I should rise and you should not, I'll gently rise and I'll softly call, 'Goodnight and joy be with you all!' "
There was barely a dry eye as the star-studded audience stood in tribute. Joley Richardson then led her somber, elegant-silver-haired mother by the arm through the room and to their car, telling PEOPLE of Streep's performance, "It was extraordinary!"