Poshmark Fraudulent practices, Discriminatory to Seller, filing legal action Menlo Park California

I sold a brand new Coach Courtenay bag on Poshmark that i paid a lot of money for. I am an extremely reputable and courteous person, and would never be dishonest in any way. The buyer offered $200 for the purse, which I felt was fair and accepted. I sent out the purse, and it was delivered to the buyer. 

The next thing I know, Poshmark informs me that the buyer has reported the purse as being "not as described." I was compeltely confused, as the purse had never been used and was in perfect condition. When I looked at the pictures that the buyer sent, I saw that it was some piece of crap blue and white bag that she took pictures of and sent them! NOT the gorgeous tan Coach that I had sent her that she purchased!!!

My suspicion is that she took the actual purse that I sent out of the package and then put a fraudulent bag there and is trying to play it off as if that's what she received. Either that or someone at one of the sorting facililites may have replaced it, I have no clue.

What I DO know is that I am out of both the money that I sold it for, AND the purse, which was such a gorgeous purse. I am heartbroken.

Where do I go from here? We do have a corporate attorney who works for us full time, who is full-time employed by my father at his marketing corporation. If I don't receive the money that i lost during this transaction, I am 100% persuing legal action. Why should I take the fall for someone else's fraudulent practices? I am sick to my stomach!