By a female customer who flat out lies and gives false feedbacks to my supervisor. I'm the team leader of a group but I'm also helping with operative tasks - which contractually I shouldn't do. She complains about services which have already been delivered saying they're late, therefore the feedback is invalid, she cherry-picks arguments, she misreports facts, she praises her little b*tch who makes a lot of mistakes then claims they were made by others.

I know that from this introduction I sound like the company's bitch and eagle-eyed readers already have collocated me at the bottom of the pyramid as per the Gervais principle, but in reality nothing can be further from the truth, I'm the one delegating all the time but this time around I'm under siege. How do I fight back? Please note that I'm in a big corporation so I don't have much wiggle room with words and attacks.

PS: I can afford losing this job since I'm debt-free and can live off renting my apartments so I can strategically be bold.