I ish we nknew when the image was taken.
If it was taken at her daughter’s home that evening then the family might know how she injured herself.
She could have scraped her home leaving home , blotted it with a tissue , the bandaged it at her daughters home.
Elderly people have skin that is like tissue paper . And with NG having heart problems more than likely she is on blood thinners or aspirin that will make a small scrape bleed like crazy.