The Father of the Bride actress's book, Where the Light Gets In: Losing My Mother Only to Find Her Again, debuts April 5
“He’s been amazing,” Williams-Paisley tells PEOPLE. “More than anything, he keeps me laughing. That s the best. He’s got this dry sense of humor.”
When she and Paisley, 43, got engaged in 2002, she and her family began noticing subtle but surprising changes in her mother, Linda Williams, who had worked as a foreign correspondent before she became a top fundraiser for the Michael J. Fox Foundation for Parkinson’s Research. They weren’t sure what was going on when she had trouble pronouncing words and signing her name – and asked if Starbucks served nachos.
“She started showing signs when she was 59 and it took a few years to figure it all out,” says the actress, 44.
Williams-Paisley chronicles her family’s journey with her mother’s dementia in her candid, heartbreaking and ultimately uplifting new memoir, Where the Light Gets In: Losing My Mother Only to Find Her Again, out April 5.
In the book, she talks about a sobering 2005 Christmas gathering at her home in Nashville when her father, journalist Gurney Williams, told her, her sister, actress Ashley Williams, and her brother, Jay Williams, that their mother was suffering from a rare, incurable form of dementia called primary progressive aphasia.
“I thought, this really doesn’t make sense,” she says. “No one in our family has ever gotten any kind of dementia. My parents are very smart. Sharp, funny, witty.”
For more on Kimberly Williams-Paisley and her book on her mother’s dementia, pick up this week’s issue of PEOPLE, on newsstands Friday
As the years wore on and the disease spread through her mother’s brain, she became more accident-prone and enraged – and began to lose the ability to communicate. She also had trouble with daily tasks, like dressing herself.
Fearful that her mother would hurt herself and others, and concerned for their father, who was exhausted from caring for her around the clock, Williams-Paisley and her family made the hard decision to put her mother in a long-term care facility in 2012.
“That was the hardest day of all of our lives,” she says. “It was just brutal and it probably always will be. Just the feeling of inevitability and also betrayal, like we were abandoning her, and that part of her still understood what was happening. That was so painful.
“I felt completely at a loss for what I could do to help but there was nothing I could do,” says Williams-Paisley, who is a spokesperson for the Alzheimer’s Association. “I felt completely helpless.”
Through it all, though, she leaned on Paisley. “He’s just seen me at my worst and handled it so well,” she says. “He’s just a team player and helps in the ways he can help.”
He listened to her when she needed to vent her feelings, watched their two young boys while she traveled to visit her mother and continues to make her – and others – laugh.
On Wednesday, he Tweeted, “Want to know if @Kimwilliamspais mom liked me much in the beginning? Read Chapter 4. Hint: Nope.”