Responses
Well, if you look at it, doctors and such makes promises even when it is just a "maybe" so it isn't really surprising, mostly because of the pressure.
Like, I am from a more advanced world, I know the disease, I have the knowledge, I am half fairy, so why can't I?
In this case and this type of manga, she will most likely be able to do it.
Though I agree with you. Hate innocent little kids. I like it when there is an older sis/bro who will hit their heads and say something like "She can't promise something like that, you brat!".

this is why sometimes I dislike innocent kids I understand where they are coming from but by asking the question they gonna put extra burden on others and Ellen girl why promise when you don't know if you could keep it or not? although I know it would work out fine but still...