Welcome to PsychCentral, jekka. My condolences on the impending loss of your grandmother. Your post took me back many years ago to the loss of my grandmother. One additional forum, here on PC, that may be of interest to you would be the coping with emotions forum. Here's a link:

https://forums.psychcentral.com/coping-with-emotions/

And then here are links to 3 articles, from PsychCentral's archives, that hopefully may be of some help as you struggle to come to grips with this distressing news:

Preparing for Grief

On Grief, Loss and Coping

11 Kinds of Therapy to Help You Grieve a Loss

My best wishes to you...