It refers to the grammar, style or whatever that is related to her (the author's) writing skills. I found the text you are working on (was tough.... had to sign up with NYtimes.com and all the works...;p) Here is the relevant paragraph so others can get more context:

I never met Miss Gould. But deep in a box at home are the proofs of articles I once wrote for The New Yorker, and in the margins is the handwriting of Eleanor Gould Packard - the magazine's venerable arbiter of style, who died on Sunday at 87. I thought I knew a lot about the English language at the time. I had a Ph.D. in English literature from Princeton, an old-fashioned kind of doctorate with an emphasis on literary history and textual editing. So it came as a surprise to see those proofs. Broader questions had been settled. But it was clear from Miss Gould's annotations - her very direct strictures - that a few details of syntax, usage and logic still needed to be fixed.