A mother receiving treatment for her second round of cancer has lost her daughter, aged 11, to leukaemia.

Frances Thompson was diagnosed with bowel cancer last year and was recovering until another tumour was found in her liver.

And while receiving chemotherapy to fight the cancer, her daughter Katherine became unwell over the Covid-19 lockdown and was diagnosed with leukaemia.

Leukaemia is a cancer of blood-forming tissues, which hinder the body's ability to fight infection.

Katherine was sent to Christchurch from Southland for treatment, where she caught a fungal infection, a Givealittle page for the Thompson family said.

Gravely ill, the 11-year-old returned to Southland and was for a time receiving palliative care in Invercargill Hospital. She died on June 26.

"We cannot comprehend the pain and grief you are facing during this time," a post on the Givealittle page said.

"Our thoughts and prayers of support, love and strength are continuing for Frances, Amelia, Jack and family.

"Life is not measured by the breaths we take, but the moments that take our breath away. Rest peacefully beautiful girl."

More than $14,000 had been donated by around 300 people in the 13 days since the Givealittle page was created.