I'm so sorry. Even though you know the time may be coming you can never prepare yourself for it. I can barely remember my great grandmother. Take comfort in the fact that you had a lot of time with her, and got to know her and hear her stories (and I bet she had quite a few!). You and your family are in my thoughts and prayers.
So sorry for your loss I never knew my great-grandmothers, and was only 2 when my great-grandfather died. Rob's great-grandmother is 98 this year. She's sharp as a tack, and made a roadtrip from Colorado to South Carolina for our wedding with Rob's grandfather. It was nice getting to know her, but so sad when they kept talking about how it was probably her last trip!
I lost my great gpa last year and I didn't even really know him! Im so sorry about your loss! It can't be easy... I dont know what I would do if my gma passed... she 78 and it better health than me! & for you during this most difficult time!!