Michelle Christie has just finished the London Marathon but on Monday she will be running another 26 miles in Belfast.
The Portrush woman is taking part for the Northern Ireland Children's Hospice, where her little girl Amelia received care.
Amelia was born with a life-limiting condition, and she received end-of-life care at Horizon House, before she died in October aged 18 months.
Michelle has raised £26,000 so far, and said she feels privileged to be fundraising for the charity.
"Amelia had a very short life, but most of our good memories are in the hospice, so it's a charity that I hold very close to my heart," she said.
"I feel very proud that I was able to raise as much money as I can for them."
The Portrush woman is ready for the challenge of running two marathons so close together, telling UTV what she thinks about when the going gets tough.
"I keep reminding myself that my pain is only temporary. Amelia suffered every day," she said.
"I'm thinking about how good everybody has been about sponsoring me and I can't not finish it."
The hospice provides specialist care to around 600 life-limited children in Northern Ireland, and Michelle said being able to help others is a good feeling.
She continued: "Our journey with Amelia is over, but somebody else's is beginning, and the support that we received from the hospice meant more than anything in our darkest hours."