Which is a little disappointing, for sure. But in her big, long email, she did bring up one issue I think might be a genuine concern: the manuscript may need to be "Americanized." I mean, it's pretty obvious that I'm Canadian. Besides just using British spelling, there may be other subtle grammar issues.
If the other agents who have the manuscript bring it up, as well, I'll have to do a substantial revision for this. /Sigh.
Let's hope for better news on my other submissions!