It sounds like she had the courage to see Christmas, and the grace to know when to go. I hope I can be so brave.
We have a similar experience. A close family friend, who worked as a school administrator, got breast cancer and it spread to the liver. She fought for several years but the disease took over. This Christmas, she was very ill but used all her strength to see one last Christmas Day. The school closed down her road and the school marching band got a police escort and played at her bedroom window on Christmas Eve. She was too ill to come downstairs, but it raised her spirits. She died peacefully on January 3rd.
She has an 8 year old daughter and the husband died 3 years ago. That child is in my thoughts, and the parents were so wonderful that I have great hope she will remember them and overcome the pain to develop into a terrific adult.