From what I've gathered the contents of the email were largely like "Either we do XYZ or we can work towards setting a date where I leave the company." So it is open to interpretation and vague enough that both sides can get their interpretation in. The way I phrase it to myself is that she was fired for threatening to resign. IE, that relationship wasn't good to begin with and this was just the last straw that pushed them to severing it. I suspect that people who try to claim she was fired/that she resigned don't focus enough on the broader context where that relationship was bad in the first place. This doesn't seem like it was something out of the blue, this has definitely been going on for a bit, so given that, which party took it over the line to breaking up their employment relationship seems like a detail rather than an important fact.