My understanding of what she wrote is that there are not that many people who control most of the money in the valley. These people are all connected. She seems to feel (again, my understanding of her writing) that the people she was working with represented a fairly large percentage of the movers and shakers.
From that perspective, I can understand how she might feel that her personal experience was a good representation of sexism at the top levels of business in SV. I admit to having absolutely no idea if this is correct.
The more interesting question, from my point of view, is whether or not this is really a "sexism in the valley" issue, or if it's a sexism in the halls of power issue. I get the impression that she feels that there are a few powerful people in SV who are perpetuating the problem, but I actually think the problem is much deeper than that.
While I've seen problems with sexism (and racism) in my career as a programmer, it's been pretty rare. On the contrary, when I've been privy to the goings on higher up the ladder (or over in sales) it has shocked me. When I talk to people in other industries it's been similar. My friends who worked their way up in large hotels have had some incredible stories.
So, focusing on SV is doing a bit of a disservice, I think. I can fully appreciate that she can't talk about things for which she has not experience, so SV is what she feels is in her vision. But I don't think it will do any good unless we realise that people in power often feel that they can take whatever they want. And often they are unfortunately correct.