I doubt if you can change the fact that she's not detail oriented, but what you can certainly do is to help her learn techniques that lower the chance that she misses a detail which is important. For maths questions involving calculation, I've had some success lately in getting my DS in the habit of doing a "reasonableness check" after he's done the calculation. E.g., if the "mean" of a set of numbers lands below them all, that would fail his reasonableness check and lead him to realise that he'd missed a number out if he'd made that mistake.
