Earlier quoted context omitted.
> Politely but firmly told her ... Fuck off Your story makes you sound abrasive and unpleasant. If the story played out the way you tell it, she obviously was a bad actor and did something terrible. (And yes, there are definitely some people who will play control games with any little bit of power they gain.) It's difficult to sympathize with you, though, when even your telling of the story makes you sound difficult…
You missed one word - "politely". One can be polite and still convey the intended message :-) She obviously got it, hence the revenge.
I also don't believe a politely delivered message can result in a 3-month plot filled with false reports, culminating in job termination. How does that play out? "Wow, he's so polite all the time! I'll fuck him over anyway because I'm pure evil! And I've got nothing better to do, so I'll keep at it for months!"