There's a really lovely sentiment behind this - it's a very powerful idea. But there's also something very hard and unsympathetic about it. 'dead grandmother' really leaps out of the page and knocks me cold, and it takes a re-read or two to get over it.
Do you think there's a softer, more gentle wording you could use? 'grandmother's ghost', for example, lacks the... callousness, while still telling the same story.
i really went with my gut with this one - just wrote down what came to mind. i do understand the point you're making and i agree that it is hard and unsympathetic, but i also think that's what makes it powerful. like someone else said, it's like "a punch in the gut". i don't mean to offend anyone with my word choice :S i'll think about it though, see if i can come up with something i like. thank you very much for the feedback!