I dunno, too many different directions you could go with this one. Her response is mild enough that I don't think you should assume the worst; maybe just tell her you're sorry and didn't realize how your question would come off.
At the same time, I'm always very hesitant to apologize for something I feel wasn't wrong, because a lot of women see that as a trait to be taken advantage of. But if she's as stressed as she says she is, maybe you just need to tread a little lightly.
If this is a constant thing, though, then definitely run for the hills.
“The whole concept of a macronutrient, like that of a calorie, is determining our language game in such a way that the conversation is not making sense." - Dr. Kurt Harris