I have seen literally no evidence that she was harassed simply for being a woman.
To me the uptick in personal insults seems obvious, and uncorrelated to a long history of questionable decisions by Reddit admins. Although I think her being labelled as a feminist false accuser is as much the reason as her being a woman.
Pao was the face of reddit as CEO and had to rightly "face the music", not because she's a woman. I find it incredible to see things boiled down to "they hate her cuz she's a gurl".
Well, the litmus test can't be simply whether the harassment solely targeted her gender and nothing else. Sexism (and other forms of bigotry) have a more insidious nature to them.
I don't think she was responsible for nearly so much of the stuff Reddit reacted negatively to over the course of her tenure as some would think, but I think the primary blame for that perception lies with Reddit's leadership as a whole and their astounding lack of communication to their audience. They knew that Pao had been the subject of a high-visibility lawsuit heavily steeped in social justice implications, which she rather badly lost - it doesn't take a PR genius to think that if you start introducing sweeping social justice-driven changes to your site while she's in office as CEO, people are going to presume that she's the one driving them. That could have been trivially defused by saying "This was a decision made by our board" or "This initiative is something we've been working on for the past 3 years", rather than just sitting by and letting the bogeyman grow and grow.
As another example, as best I can tell, Ohanin let Pao take all the heat for Victoria Taylor's firing, and then clarified that he was the one who made the decision to terminate her only after Pao had resigned. A huge amount of unrest could have been deflected off of Pao if Ohanin had said "Hey, I'm the one that made this decision", but that wasn't said (if I'm wrong, please let me know; the first reference I saw to this admission was timestamped around ~1h ago). In fact, reddit's leadership as a whole was extremely wishy-washy and vague about the whole thing, despite the fact that it upset the volunteer base that makes reddit usable enough to incite mini-revolt.
Leaping to claims of sexism seems lazy and just a little-too-convenient for me. I think that if her husband had been in the CEO role and the same things had happened, given his PR image problems, you'd have seen the same magnitude of criticism and outrage (but then, of course, people would level claims of racism as the cause, which I think would have been equally as wrong).