I'm more interested in the answer to question 3
"Is it even something we ought to be concerned about?(I won’t dignify that last one with an answer.)"
I'm guessing that the reason the author won't dignify the last one with an answer is that she feels the question is rooted in deep sexism, or dismissal of a serious problem. And I'd agree, discrimination and/or stereotyping that leads to women giving up on CS is a serious problem.
However, a slightly less extreme version of this question is important: "is it possible women are finding better professions than software development". As an exercise, consider the case of a young woman who has entered your office to talk about whether she should pursue a career as a programmer or apply to medical school with the ultimate goal of becoming a cardiologist. Make sure you address longevity of careers, pay, stability, social standing, attrition rates from graduate programs, and so forth.
I do think it's very important to ask why women aren't going into CS. To the extent that stereotyping is responsible, yes, we should fight it. It clearly is a factor.
But young women are starting to outperform young men academically. A recent RAND study concluded that young Americans are rationally avoiding PhDs in STEM fields because they are not competitive with the professions (where women are closing the gap rapidly, and in some cases creating a gap that favors women). In this case, avoidance of these fields may simply be one more way that women are making better decisions than men. Programming careers can be very rewarding, but they're hardly the only game in town, so it makes no sense to analyze it in isolation.
If women aren't going into CS, what are they doing instead? Should we be telling young women who choose nursing, law, accounting, and medicine that they would be better off studying CS and becoming programmers? If anything, we might want to encourage young men to look at what young women are doing and learn something from them!