English articles are probably the most difficult aspect of writing for non-native speakers to master. There really aren't very good, concise rules and so many uses are complicated or idiomatic. I had a classmate from Japan whose English was impeccable who would ask me about article rules and challenge me to teach him all of them. I never won that challenge - every day he'd come up with a new sentence to stump me.
Realistically, I wish there weren't such a stigma against non-native speakers. If a decent editor can make sense of the writing, there isn't any reason she should be treated differently than other writers. Native speakers need to have their writing edited as well. But I see what you mean about the practicality of the situation in terms of how she's perceived in the workplace.
There are resources like
this one, but again, there are more rules than are presented there and some of the hardest situations to explain are those in which no article is used or things are used as abstractions (Think of the sentence
The invention of the computer revolutionized the American workplace.)
My preference, rather than providing her with a huge number of counterexamples and a giant maze of rules, would be to provide her with lots of chances to get input of positive examples. The best way to do this is through extensive listening and reading. The best second-language speakers are the ones who listen to/read a lot of the target language and then speak/write by imitating the style that they've been exposed to. If you have the time, you could help her out by finding published articles in the style she's expected to write in and isolate examples of the kind of sentences she needs to imitate. Have her write her own sentences based on those patterns, and reinforce it every day. Maybe even send her an email in the morning saying "Please write me a sentence that uses
the like this sentence does and send it to me by this afternoon."
