Hmm. What does your adopted grandma say/do? It sounds like your being friends and loving her always, etc., that a lot of that is on your side/what you need? It could be since you're moving away you don't want to get hurt, kind of like when one changes jobs and are feeling guilty for moving forward with your life?

But I don't know the relationship, how it came to be and why you adopted her and what she says/does, how she feels about your going back to school, etc.