Book Board Chat

Need some advice about problem with buyer who put claim in with PayPal. She returned one of four sterling Franklin Mint plates bought from me, claiming she had it tested & it was not sterling. Plate she returned was not the one I sent her - she pulled a "switcheroo". Returned plate was scratched, the one I sent was perfect & it had other signs of being a replacement. PayPal has the info from me, including test I had done today on plate at a local jewelry store which showed plate to be sterling. Tested on the underside, a little of the non-tarnish coating the Franklin Mint uses was removed. She could not have tested plate as there was no coating removed when I received it from her. She asked me not to send plate back to her this Monday, but wait for PayPal to make their determination. I had emailed saying plate would be returned on Monday if my test showed it was sterling. Thats my question -Should I mail the plate back on Monday? I don't want to keep both the plate & her payment. Iris