But for how I see things, this is primarily a story about growth. And death is a part of growth just like love, work, school, friendships, rivalries, happiness, sadness are.
From this perspective, I wouldn't see it as out of context. I'd have a different kind of qualm, the fact that so far Grandma hasn't really played a great role in the story (if we except her grand debut in episode 1 she didn't do much after that, other than becoming fonder of Ohana and some little details about her past being shown). So perhaps, if that is going to happen, we'll have a set up that will warm up the audience towards her much more. In these kind of shows, they usually don't kill a character for the sake of it.
Here's an analogy from "Summer Wars" , the movie. Spoilerish though, so don't read if you didn't watch that movie and/or plan to.