Mercari complaint: Conplaint about seller

I put up some items for sale on mercari. The person is ambr3 who also sells items. She purchased 2 shirts from me. She contacted me saying that there were some underarm pillings and asked for a refund. The items were in good condition but I didn’t want to argue. I told her that I would accept the refund and fir her to donate the items. She also said that she didnt have to return them which was unfortunate to me. That is why I told her to donate them. didn’t know she was also a seller until recently and what do I find. The 2 shirts listed in her website for sale. I put through a complaint but never heard anything from mercari and no way to contact them about my issue. I think mercari should give me the money I would have earned from this sale. I have copies of our communication and the items of mine that she didn’t pay for but is selling now. She has an extensive website so mercari won’t shut her down because she makes them money