How long has she got?

its very hard, both to come to terms with, and to predict time left, instead of doing that, leave that aside. Just make your grandmother as comfortable as she can be, but dont shower her with constant duties, or behavour out of the ordinary, as she will both want her dignity and to know your not all falling apart over this. Just spend good time with her and also give her reading or tv / films she likes to take her mind of things . Im very sorry btw.