So this gets into nuance and I will preface this with, we don't know what her email specifically said.
If you give your company a date for the cessation of your employment, that is giving notice. If you say I "will resign if", is saying that you will do something in the unspecified future.
So if you give your two weeks notice you have formally turned in your resignation. In your example I would agree that they just changed the timetable. If you haven't given your notice, and they terminate your employment citing an email you sent, you have been fired.
By all accounts she didn't submit her resignation, she simply said that she would. Sometimes situations like that result in the person getting cold feet, or the two parties working out a compromise. Maybe things would've always ended up the same way, but either way Google didn't wait for her to actually resign.