Have you ever been in a 100-level CS course? Granted, it's been a while for me, but they're generally full of 18-year-olds who lack a certain amount of social grace. IME, most people are pretty okay, but there was a notable minority of people you just don't want to spend time with: annoying, obnoxious kids who feel the constant need to correct everyone around them (including the instructors) to demonstrate how frickin' smart they are, and who don't realize they're also surrounded by other smart people who aren't as annoying and obnoxious. And, IME, many of these people actively make young women uncomfortable with their advances and behavior.
There are still lots of liberal arts schools that are very much gender-segregated (Wellesley, Smith); I can't think of any "women's" tech schools. I wonder what the CS classes and enrollment is like at places that are more-or-less women-only.
Of course it also starts before college enrollment. AP computer science courses in high school have about the same gender ratio (19%). [0] Those would probably contain the same minority you mentioned, a few years younger.
[0] http://www.nytimes.com/2013/03/08/technology/computer-coding...