Audrey was married to Geisel in 1968 (the second marriage for both of them) until the author/illustrator's death in September of 1991 at the age of 87. According to Variety, she had quite the influence on her husband's writing, reportedly encouraging him to pursue lofty ideas like pollution, conservation, and nuclear war in publications like The Lorax and The Butter Battle Book.
"Every book had something that was morally important, but rather masked, but always there. Otherwise, Ted would not have said from time to time, 'Am I getting preachy?' He did not wish to seem to be preaching," she once remarked during an interview with Reading Rockets.
After his passing, Audrey took over his estate, overseeing adaptations (mainly movies) of her late husband's most famous publications in a producing capacity. All of this was done through Seuss Enterprises, an L.P. founded in 1993 that licenses out "Seussian" characters to studios, production companies, and other paying customers.
Audrey also gave away over 4,000 pieces of Seussian memorabilia to UC San Diego after her husband passed away. Drawings, letters, and more are now housed at the college's Geisel Library, established by Audrey in 1995 with a $20 million grant.
She was not a producer on the live-action versions of How The Grinch Stole Christmas (directed by Ron Howard) or The Cat in the Hat (directed by Bo Welch), but hated the latter so much, that she refused to let any more live-action adaptations be made out of her husbands books. As a result, all subsequent Dr. Seuss film adaptations have been animated features: Horton Hears a Who! (2008), The Lorax (2012), and The Grinch (2018). Ms. Geisel served as an executive producer on all three.
"I just know that what he left as a legacy is the fun of learning when you don't know you're learning. I think the legacy is that he pleased children," Audrey said in the aforementioned interview. "He pleased the parents of children. And he's here for all time."
While Audrey had no children with Geisel, she is survived by two daughters from her first marriage.