Personally, I'm not sure it can be easily recorded. If it can be, perhaps incorporate themes that are important (such as a family group picture if its' not too complicated) to her rather than the stark pain and deterioration, which isn't telling the whole story.

Perhaps after she passes, you could build a slideshow of family photos that do tell the whole story. The theory is, that it's already recorded and you just have to assemble it. I've done it twice, and helped others with it. It can be tough and rewarding, and doesn't require the same social graces that one might want to have when photographing someone's last days or hours. It's not analog in that you'll probably do it with a computer, but you'll be carefully handling lots of great and meaningful analog photos created during the course of her life. It's truly telling an important story with photos, and family and friends will appreciate it (perhaps to the point of being overwhelmed by memories at first), people will learn new things, and it can complement the life celebration / funeral events in many cases.