thanks gubaba for explaining the nausicaa parallels, and i think it's likely we'll see something similar in MF.
i don't think though that ranka is fully aware of the risks in seeking out the vajra, but it is a brave thing to do nonetheless.
unlike you, i am firmly in the sheryl camp, but still, i find no reason to hate ranka. heck, i don't even dislike her. it's more like, she's just not my type. regardless, ranka is an interestingly crafted character, if perhaps a bit annoying at times, but a good one nonetheless. i'd even go as far to agree with wolfx that in a sense she's purer than most, and we get to see how she sheds some of that innocence as she matures, in both good ways and bad, and some forced on her whilst some willingly.
as for nanasae, you probably meant "well-drawn"