"I have my own theories," the 61-year-old actress said on the May 9 episode of CBS Sunday Morning, "but I've been told not to express them."
In February, CBS announced the beloved sitcom would sign off for good after its eighth season—news that came as a great shock to Allison. And saying goodbye to her character Bonnie won't be easy for the star. "I hate change," she said. "I get afraid—I always have—to let something go and not know what's next."
"You know, it's one thing to be part of a show that entertains, which in and of itself is a wonderful thing," Allison, whose brother Hal Janney passed away following his own battle with addiction, said, "but to also have an impact on people who are in recovery, or people who have loved ones or family members who are going through it, to make recovery a more approachable option."
During a March episode of The Late Late Show, Allison said she wished Mom had "at least another year" to give the writers time "to ramp up to the ending."
"We sort of found out sooner than we thought we would," she told James Corden. "We thought, Surely, they're going to want more Mom. And they decided not."
At the time, she chalked the cancelation up to money. "I know that [executive producer] Chuck Lorre is writing the final episode, and we're right now filming the third-to-last episode," she said. "I'm having a lot of moments where I'm just standing on set, taking it in and looking at all the faces I've looked at for eight years."
The final episode of Mom airs on CBS May 13 at 9 p.m. EST.