Online tributes to mother-of-two have celebrated her advocacy and success in raising millions for research - coming as she battled breast cancer and received treatment in a palliative care unit after the illness spread to her lungs, liver, pelvis, spine and knee.

Her brother, Gold Logie-winning actor Samuel Johnson, announced the 40-year-old's death in a Facebook post on Friday night.

Details of her funeral are yet to be released.

Some Facebook users have posted a single red heart emoji in memory of Ms Johnson, adopting a trend that began for breast cancer awareness earlier this year.

Wilkinson, co-host of Channel Nine's Today Show and editor-at-large of HuffPost Australia, called Connie Johnson "extraordinary".

"There are no words that do justice to the beautiful, heart-breaking story of #ConnieJohnson, @samueljjohnson78 and their extraordinary determination to one day find a cure for the cancer that yesterday, finally took Connie's life," she wrote on social media.

"May you rest in sweet peace Connie, knowing you have left this world a far far better place for your heroic, inspirational journey."

More than 140,000 people have interacted with a Facebook post announcing Connie's death.

"It was so beautiful. We laughed, we cried, we sang stupid songs from our childhood to her, which she loved (mostly!)," Mr Johnson wrote on the Love Your Sister charity Facebook page.

"Thanks for everything, Connie Cottonsocks. It was my pleasure to be your Sammy Seal."

Connie Johnson received the Medal of the Order of Australia from Governor-General Sir Peter Cosgrove just days before her death in a Canberra hospice.

The award, recognition for her campaigning and advocacy for cancer suffers, came after her brother quit acting in 2016 to focus on fundraising and care for Connie.

She launched the charity organisation Love Your Sister in 2012 in an effort to raise funds for cancer research.

Together they raised millions for cancer research, including more than $2 million in May when a Canberra netball court became a sea of silver five cent pieces for Connie's Big Heart Project.

In August, Connie spoke to Fairfax Media of her determination to stay alive for her younger son's 10th birthday later this month.

"I've been told I really suck at retirement," she said at the time with a smile.

"The memories from the Big Heart Project sustain me every day.

"It's mind-blowing to know that our community is so strong and I'm part of it. I'm so proud to be a Canberran...It's real, it's real."

In her final days, Connie's focus had contracted down to her husband Mike and two children, Willoughby and Hamilton.

The Johnson family has asked for tributes to be posted at loveforconnie.org.