The actress was found dead Sunday in her Colorado home

Credit: Everett

Patrick Dempsey has spoken out about the unexpected death of Amanda Peterson, his costar from the fan-favorite ’80s teen comedy Can’t Buy Me Love.

The actor, 49, took to Twitter to remember the actress, writing, “In my memory, she will always be vibrant and young. Gone too soon. Sending my thoughts and prayers to Amanda’s family.”

Peterson starred as high school cheerleader crush Cindy Mancini, whom Dempsey’s character, Ronald, pays to pose as his girlfriend in the teen romance film. The pair were in their 20s when the film debuted.

Peterson was found dead at 43 at her Greeley, Colorado, home on Sunday. The autopsy report is still pending, but her mother, Sylvia, believes her daughter’s sudden death may have been related to various health issues, including sleep apnea.

“She was in bed, and she’d had a wonderful day, and we were planning on a dinner the next day,” Sylvia told PEOPLE on Tuesday. “So it was just a very, very big surprise.”

“She was just so much fun, and she was just great,” Sylvia added. “She had a cute sense of humor [and a] love of history – just a very, very cute person.”

She is survived by her second husband, David Hartley, and two children, and was reportedly working on an autobiography.