It wouldn't. :~) But it would be a very natural thing, if you were growing up and everyone were telling you that fairytales etc weren't real. If Sarah was told by everyone that she imagined what happened, she might study stories as a way of trying to convince herself of that. Being a teenager includes wanting to fit in, and having travelled to a magical land isn't very normal...

Or it might work the other way round - she might start out studying literature as a way of proving to herself that her book and what's in it really was real. Or just because of her love of stories, I don't know. I just see it fitting her. (Literature student here, in case you were wondering. :~D)

Although to be fair I like your idea of making her an engineer and focussing on hard science instead. I'm looking forward to seeing how that turns out.