"My mother passed away this morning just a short time ago, peaceful with my sister by her side, in her sleep," son and fellow actor Corbin Bernsen said Wednesday on Facebook. The network also confirmed her passing.
"I was going to visit this afternoon, thought I had time," he wrote. "Reminder to self -- time is a precious thing. I too am at peace, however. I said my goodbyes several times over during the last few weeks. I'll go one last time now for a gentle kiss, a final farewell for this lifetime.
"She has been a blaze her entire life, that beacon, that boxer I spoke of earlier. She went the full twelve rounds and by unanimous decision ... won!"
On Twitter, Bernsen had been chronicling his mom's health struggles with an undisclosed illness since mid-April, thanking fans for their love and support and posting pictures of Cooper in the hospital -- including one in which she was playfully flipping him the bird with both hands. "Only 4 those with sense a humor ... Mom wanted 2 share a photo, I asked 4 thumbs up, got this ... she's on the mend!" he wrote at the time.
Cooper was the "Y&R" cast member with the longest stint on the series, having joined six months after it launched in March 1973, according to Los Angeles Times wire reports.
"God knows it's claimed a big part of my life," she told the Associated Press as the show marked its 40th anniversary in March.
Read Cooper's full obituary here.