I think you can still iterate and stay in touch. Indeed, I think that's the best way to iterate.

The problem wasn't the copy changes. It was not demonstrating sufficient respect for the other person's work. If he had emailed the colleague with a note as he started tinkering ("Great work on the landing pages; I'm going to see if I can tighten the prose up a bit.") and then sent her the diffs, there shouldn't have been any upset.