Your student didn't want to be involved in programming competitions because they are unglamorous, not because the environment was hostile to her, as your story demonstrates.
My student didn't want to be involved with a programming competition because she didn't know:
1) She was an amazingly good programmer relative to the field.
2) Programming competitions can be fun.
It's MY job as her senior to impart that knowledge.
The fact that no other professor imparted that knowledge is a problem--she should have had several professors imparting this knowledge. The fact this was not true shows that such things as "competition teams" are NOT meritocracies.
I had to practically threaten my best student (a female) to get her to go to a programming competition.
At which she proceeded to beat 80% of the teams by herself by answering 4 of the 10 problems outright. And then the rest of the team answered 2 more. They did quite well.
Her response: "That was fun. I'm pretty good at this."
<facepalm> Yeah, that's why I made you go.
I didn't shove her there because she was a female, I shoved her there because she was BY FAR the best student in my class. And the first time she showed up for a competition prep meeting, it was stupidly obvious just how much better she was than the rest of the team.
Some professor gave all of those students on the team a shove to get them there. Other professors had her as a student. None of them gave her a push to go do the competition. Why not?
That's the kind of thing that fills or drains the pipeline.
And that was college, a point where women finally aren't quite so worried about peer pressure. I imagine if I was teaching high school, I probably would have had to pull her parents in to exert enough pressure to make her go.