This doesn't make the article true, of course, so absent corroboration we must rely on internal evidence to assess credibility. To my eye, such internal evidence indicates that the story is credible. In particular, the details in the article explain for the first time exactly why Theresa Preston-Werner would have met with Julie Ann Horvath and why the conversation turned so quickly from casual to serious. [1] It also explains more credibly the relationship between Horvath and the allegedly "harassing engineer".
It's tempting to try to shoehorn these incidents into the "sexism in tech" narrative, but we should be willing to concede the point if the shoe doesn't fit. My own guess is that several people screwed up, there were misunderstandings galore, and there's plenty of blame to go around.
[1]: http://techcrunch.com/2014/03/15/julie-ann-horvath-describes...