What to do? I'm a new seller

Buyer contacted saying the jeans she received from me were stained, but I don't remember seeing stains when I listed them. These jeans sat in my closet with my other jeans and in another stack of clothes that I was selling. There's no way I could've gotten "oil" on them. Unless it happened during shipping, idk. I'm hoping buyer is just mistaking the acid design for stains and there's no real stains.

I don't accept returns. I'm a fairly new seller (26 sold). Could this be a scam? I added pictures for reference. Lmk if you're seeing something I'm not!!