Author B advised her not to worry. Most readers wouldn't notice and those who do will think they've been let in on a delicious secret.
Since I was eavesdropping (rude in itself) I couldn't exactly plow into the conversation and provide my opinion. (I know--shocking that I actually kept my big wazoo shut!) But this blog is mine so I can spout all my wisdom here. So here goes:
Hey, Author A! Is there a specific reason the story warrants the change? Are all blond, blue-eyed men being annihilated and it's up to the green-eyed auburn-haired lady to save the hero? Because, otherwise, I'd advise against insulting your readers by underestimating their intelligence.
See, I'm not just a writer. I'm a reader. A big one. I was a reader long before I became a writer. And I can tell you right now, there've been cases where a character in one book undergoes some kind of metamorphic change in another. Never once did I think I was in on a "delicious secret." Instead I thought, "Here's an author whose research is so poor, she can't even go back to her own story for fact-checking."
Where do you stand? What's forgiveable in your books? What makes you think the author was lazy?