I personally feel that women get turned off to CS and in general tech courses because they're male-dominated and usually somewhat misogynistic, which makes being in CS classes and interacting with CS majors sometimes unpleasant and encourages them to do something else.

In general, women are perfectly intelligent and capable of studying (see: women in premed, women in law, etc, etc).

CS isn't some mystical major that's harder than every other major ever (me, I'm scared of business majors; those guys are cutthroat), and I don't think "women can't commit themselves and women can't study the same way and women don't do research" is really a good explanation for why there are fewer women in CS than there are in premed.