She clarifies in the comments. She says that she didn't mean to imply that this was because they were women. And I think she should have gone into more detail because this is the anecdote that defends the title of her post, and this snippet sounds terrible without context.

But my take is basically she says when she was confronted with an overwhelmingly male pipeline she tried increasing diversity by increasing the acceptance rate of female candidates. She then tells a story of how this backfired and increased negative stereotypes about female engineers. I don't think she believes women in general lack or drain energy, just the few she hired for her start up.