A short sequel to the film is in the works for charity, set to debut on March 24 for Red Nose Day. Neeson, Colin Firth, Hugh Grant, Rowan Atkinson, Thomas Brodie-Sangster, Martine McCutcheon, Knightley, Andrew Lincoln, Lucia Moniz, Chiwetel Ejiofor, Nighy, Marcus Brigstocke and Olivia Olson will all be a part of the upcoming project, with Neeson and Brodie-Sangster already photographed in character.
But for Thompson, revisiting her role would be "too sad."
"[Director] Richard [Curtis] wrote to me and said, 'Darling I can't write anything for you because of Alan' and I said, 'No, of course you can't, it would be sad, too sad, it's too soon,'" the actress told Reuters at the UK launch of Beauty and the Beast on Thursday.
"It's absolutely right, it's supposed to be for Comic Relief and there isn't much comic relief in the loss of our dear friend really only just over a year ago," she added. "We thought and thought but it just seemed wrong."
Rickman died of cancer last January. He was 69 years old.
While Thompson says it was "absolutely the right decision" to leave her character out of the upcoming short film, she's definitely looking forward to tuning in. "To revisit the wonderful fun characters of Bill Nighy and Hugh Grant and all of that, that's fantastic," she gushed.
Though Thompson won't be a part of the sequel, her character did receive a little closure. During a 2015 live tweeting session, Curtis finally revealed what happened to Thompson and Rickman's characters, after the discovery of Rickman's character's affair.