Kirsty, 29, died before she had time to prepare her two children, Ebony, six, and Adam, two.
She had started suffering from headaches and eye problems around six weeks ago.
A routine blood test revealed abnormalities in her liver enzymes and bones and Kirsty, from Annfield Plain, County Durham, was referred to the University Hospital of North Durham.
The part-time office administrator was sent to a lung specialist after tests were made, but her breathing was so laboured she was admitted to hospital.
She was allowed home over the Easter period but was back on a ward after she continued to struggle with her breathing.
On Wednesday April 3 she was diagnosed with advanced lung cancer which had spread to her spleen, liver and glands in her neck.
She died the next day, before she could start chemotherapy.
Her mother Wendy was with her when she died, but Kirsty didn't get chance to say a proper goodbye to her daughter and son.
Her grieving mother Wendy, 49, of Stanley, County Durham said: "The doctors said they had never seen anything so aggressive. She was diagnosed on the Wednesday and on the Thursday she died.
"She had never smoked in her life, she never touched them. She was so healthy and went to the gym and liked keeping fit.
"I am making a memory box for the kids, she said she didn't want them to forget her.
'It is so difficult, I have cried for a week but Ebony says some sweet things that are keeping us strong."-of-two-