Because for two years she said the opposite? She is, was, or is and was obviously lying, it is just a matter of when and how much. Was she lying before when she said everything was awesome, or is she lying now?

You could play the super long odds, everything was AWESOME for the past two years, but just turned awful. Then she was only lying now (because "I've been harassed by 'leadership' at GitHub for two years..."). That would paint her in the absolute best light, and it IMHO, rather unrealistic.

You could even play the super-super long odds, and assume everything she said before was a lie (said it was good, it was actually awful) and then things BECAME good recently and she doubled-down on lying and said things were bad.

... in my case, it isn't an assumption. It is a expectation based on prior behavior.

She has previously classified someone complaining to her employer that she used foul language during a speech at a conference where she was representing her employer as harassment. This makes me question her judgment regarding what should be considered harassment.

I'll quote Lea Verou here: "not accepting something as de facto objective truth w/ no info != thinking one is lying. It's being rational instead of emotional." https://twitter.com/LeaVerou/status/445001688923914241

Here's an example:

X: The economy of Southern Portugal during the first half of the 13th century was bad. Do you agree?

Y: I don't know, I don't have enough info and absolutely zero knowledge of Portugal's economy during the 13th century.

X: are you calling me a liar?

that seems like a poor analogy to me. Try this one

Harry: I can't afford to do that

Tom: I don't know, I don't have enough info here to know if you can afford to do it or not.

Bob: Are you saying that Tom is lying, or that he doesn't know his own situation?

The big difference in this case is that while it is totally plausible for X and Y in your conversation to know literally nothing about Portugal, in my example it is not plausible for Harry to be unaware of his own situation without being an idiot. So when Tom 'withholds judgment' on Harry's situation, he is saying that evidence directly from Harry is untrustworthy - Harry is either a liar or an idiot. (I introduced the third person, Bob, as in this case Tom is Horvath and she is not the one responding to you, doubting Tom).

This is a wrong analogy because it doesn't involve grave accusations of a third party (Portugal's economy in my case and github in the other).

ok, try this

  Harry: John punched me     
  Tom: I don't know, I don't have enough info here to know if you were punched or not     
  Bob: Are you saying that Tom is lying, or that he can't recognise when he's being punched?