So, that's getting fired for cause, maybe, but not resigning. Google's official story is that she resigned. You have to stretch things pretty far to say that taking an action that might get you fired is the same as resigning. Resigning is handing in your badge and laptop and leaving the building. Getting fired is being called into a 4PM Friday meeting with HR and they escort you from the building afterwards.
I am not really even sure how meaningful an email telling your coworkers to stop working on their projects is. It really depends on the tone. When I was at Google, I used the internal social media extensively. I am sure at some point someone said something like "I'm really depressed about how my project is going" and I would reply with something like "You should join my team! I have a req!" That's technically telling someone to stop working on their project, but is a completely acceptable thing to do.
Ultimately the exact details matter, and we don't have them.