According to their research, women started out with much less confidence but by the junior year it has started to level out when the classes become more difficult for both genders. See section "Gap Between Perceived and Actual Ability" and "Confidence Gap Narrows"

Also see "Geek Mythology: Lore about Being in CS" specifically "It is important to note that most of the CS students (both male and female) we interviewed feel they do not match the stereotype: their interests are varied (including sports, theater, poetry) and not isolated to computer science. "

http://www.cs.cmu.edu/afs/cs/project/gendergap/www/papers/si....

This paper expounds more on the view that a student must be absorbed in computers 24/7 and that women's perception is that they must be this way to succeed: http://www.cs.cmu.edu/afs/cs/project/gendergap/www/papers/an... men who are not like that still feel like they can be successful in computer science under "The Non-Hacker Male" from that paper.

Based on this information, I believe the stereotypes are self perpetuating and breaking the feedback loop will help a lot. I ask that you personally help by keeping an open mind.