My first thought when reading this - and I'm not sure I've thought it through so please feel free to shoot it down - was of a book dd has, "The Gifted Kid's Survival Guide". In it is has a 'gifted bill of rights'. I can't find our copy, but one on the list that has always stuck with me is that gifted kids have a right not to have to give 100% in everything. This doesn't mean "not pass that subject", just that it isn't necessary for them to have to do the best they can in every subject. The implication was they should put in the effort for those things they value but that they have the right to only put in enough effort in other areas to enable them need to to ensure that they have the skills to support the things they do value.
I.e. if a kid is madly passionate about science, then that's where they should exert their energies. However they still need to be able to write to be a scientist and so they need to develop those skills, but they don't need to perfect them.
Obviously this needs to be applied with a dose of common sense (obviously "I want to be really good at watching TV" is not how this was intended to be read!)
I guess what I am saying, is if she's doing ok at things like writing, why not let her get adequate rather than phenomenal marks in it and up the challenge in the things she enjoys? She might even come to enjoy it later (I write for a living - not that you know from my posts - and writing IS hard if you're not interested in the subject matter).
I appreciate there might be many reasons this isn't appropriate in your circumstances, but just thought it might be a different perspective.
