But she had been cancer-free for a decade until its return when she was 32.
According to the Irish Mirror, she was told in January that her cancer was now incurable, but could be maintained.
Now husband Ed, 42, has been diagnosed with terminal pancreatic cancer, after suffering chest pain and nausea.
He is in hospice care, and has just months to live.
Karen's friend Stacey Hogg set up a GoFundMe page to help the couple make memories with their family while they are still around.
Writing on the GoFundMe page, Hogg explained: "Karen was diagnosed at 18 with a childhood cancer, unfortunately it has come back for the 3rd time, she has since been told that it is now incurable. Karen's main carer is her husband Ed.
"Devastatingly he is now fighting the disease himself. They have been through so much and more.
"They have 3 children Keeva, Finn and Erin all under the age of 10.
"The aim of the fund is help raise some money so Karen and Ed can make as many memories as possible with their 3 gorgeous babies."
So far the page has raised €9068 ($15,900).
Karen told RSVP magazine: "If you have pain, go get it checked, if you have a lump get it checked.
"It might be nothing but could be something. Don't leave it until it's too late."
Karen confessed she and her husband Ed had to go private to get their answers, and said they had put his chest pain down to a suspected heart attack he had earlier in the year.