Grandma's are mighty special people in my eyes, I'm so sorry your Grandmother is having such a hard time but I'm happy she's got you to be by her side watching over her!
You sure are on the right track in what you want to do. Uny has covered the initial list of what will be good and I'm sure she'll have lots more once she finds out what you found out from the doctors.
I wanted to give you a couple of links about juicing and how healing it is. The first one is from Dr. Schulze, the second one is a testimony written by a precious forum member who has been through making and delivering fresh juices to someone who was in the hospital. Both will solidify for you just how powerful juice fasting is and will give you hope!