A shipwreck set to happen. Polygamy and promiscuity has a nasty nature filled with backlash and risk. Dangerous gamble. Maybe her husband was more into you than her and she grew vindictive.

stuff like this is why I refuse to date nested partners anymore. lesson learned the hard way. it's hard to find a couple that the wife can actually handle it. hold your head up and explain your side

Threaten her with a defamation suit. She crossed the line when she threatened your employment with her accusations.

Why did she tell your employer?

Never let someone turn you into their unicorn. Never join a pre-established truple. Sure, those situations could, maybe, theoretically, if the wind is right and God is smiling down on you, work out. But most of the time you've just been brought in as the bandaid to an already doomed relationship and you WILL be the scape goat. You didn't have a poly relationship. You had an extended threesome with some mother ******* who couldn't let go of their failed marriage.

And this is why I've always refused invitations to join married couples. You're never going to be equal in their relationship, and sometimes you just become a convenient excuse.