It's hard to find a benign reason why the percentage of women CS majors would halve in the last 30 years while the profession as such has become more attractive.
http://www.npr.org/sections/money/2014/10/21/357629765/when-...
Now, look, this explanation may be wrong, but, no, it's not hard to imagine alternate explanations. Nice and neat conclusions in the social sciences are hard to come by. Anybody in this thread claiming that they know exactly which explanations are the right ones is full of shit.
I don't think it is hard to find a good reason why someone wouldn't go into nursing (even if this wouldn't disprove sexism in nursing). It has barriers to entry by requiring formal education, which can be competitive. The working conditions are somewhat difficult having to work irregular hours and be exposed to emotional stress as in seeing people dying. At the same time it still relatively low status, not necessarily well paid and has limited career prospects.
Of course you can argue that this shouldn't be the case. That the profession should help people dealing with stress and have good working conditions etc. Still it much harder to imagine these sort of "hard" reasons, negative things that are inherent to the profession, when it comes to programming.