The U.S. actress and television personality, 38, has been dating the 47-year-old former lead singer of 4 Non Blondes since late 2011.
Gilbert explained on Monday's edition of "The Talk" how her girlfriend last week arranged for a band to play their song, The Cure's "Love Song," while they were on a picnic in a Los Angeles park.
Perry then put on a series of shirts, which said "Will," "You," "Marry," "Me" "?" and presented Gilbert with a ring, while their mothers and friends waited nearby for Gilbert's answer, which was yes.
"I was like, 'Well, yeah, after that spectacle, how could I not?'" Gilbert quipped.
"I think that's it and it's like the most amazing proposal ever," she said, adding 1980s pop icon John Waite then showed up to sing her favorite song, "Missing You," making the experience even more memorable.
The former "Roseanne" star has two children from a previous relationship.