How old is she?
I'm no expert (on anything, really!) but here are my thoughts:
I must admit that my first thought was that maybe she's got a dash of Aspergers... As well as the people who have a significant enough situation to warrant a proper diagnosis, I believe that lots of people have a little dash or Aspergers. Not enough to get flagged up or warrant a diganosis or any professional attention, but enough to give them a few quirks that make some things more of a challenge for them than others.
My DD has always found it impossible to make a decision about anything. I have often wanted to top myself waiting for her to tie herself in knots wrangling with the pros and cons of stupid unimportant decisions. It's like she can only cope with "the perfect solution". The "it''s good enough and it'll have to do" option doesn't even come into it. When she can't achieve the perfect way ahead and there is only compromise (ie, in the real world) it's like she's paralysed by her own perfectionism. I have lost count of the times I've rolled my eyes and had to count to ten while she's agonising over some (trivial) choice or another. When I cannot stand the dithering and vascilating any longer I have been known to say "For Christsake, you're choosing a sandwich/ library book/ pair of knickers/ whatever - not a husband!".
Secondly, I do think they can grow out of these phases... My DD is now 17 and is DEFINITELY getting better, the older she gets. I think that (for children like this) when they're little, everything is decided for them. When they're growing up, they are forced to make decisions and it's difficult and uncomfortable. As they get older though, they've got more used to it and it starts to become a bit easier. They start to realise that you can make an imperfect decision and it's still ok... life continues. But this only comes with time and experience. However much we tell them that anything is ok, I don't think they "get it" until they've learned it for themselves.
As concerns school, hopefully, your daughter, going forward, will be able to choose subjects that don't require her to "write stories". This is the worst possible thing that you can ask my daughter to do. Hopefully, when she is making her options for GCSEs and certainly at A level, she'll be able to choose the subjects that are blissfully straight-forward for her. My daughter's doing Maths and Sciences for A'Levels and it's a thing of joy, never having to write an essay again.
As concerns English GCSE though (if she's not done it yet - I don't know how old she is) don't worry TOO much... English Language is quite structured and analytical and there isn't TOO much creative writing these days and as concerns the English Literature, she can approach analysing the set texts in a scientific and methodical way. My DD, despite HATING and LOATHING English, did very well in both at GCSE. Even so, she was positively euphoric about dropping them.
Finally, I'd advise you to continue to give her options, to keep things going, but lots of silly little things that don't matter, and perhaps just two alternatives rather than unlimited possibilities:
Do you fancy spag bol or spag carbonara for supper?
Shall we get this one out on DVD or that one?
Do you want to go walk the dog and then have a coffee or shall we have our coffee first and then walk him?
etc
Hope this helps a little (probably not - as I say, I'm no expert). Good luck.