This one annoys me greatly. It's downright clumsy having to write "he/she", "he or she", or "s/he" (try reading the last out loud), but writing "she" everywhere is no better than writing "he" everywhere - it assumes a gender which may be incorrect. It also tends to distract the reader's attention, leading them to think about gender issues rather than the subject of the writing.
I have no idea what we're supposed to do. I have another dilemma with forms of address: if I don't know the marital status of a lady (and why should I?) then should I write to her as Miss, or Mrs? If I choose Ms, I stand an equal chance of causing offence.
Fortunately I work in science, so I can call everyone "Dr" with little risk, and I rarely get the opportunity to use a pronoun. Stuffy journal editors get upset at the mention of something so human as a "he" or a "she", let alone (heaven forbid!) an "I". I don't write. It was written.
I write technical documents for a living. Well, actually I write code for a living; the associated documents are a by-product. I always use 'she' as the gender-neutral pronoun because it cannot give offence save to those eager to be offended. The same applies to 'Ms', which is the marital-status-neutral form of address. I decline to imagine the sort of individual who would be offended by such a form.