Seller requesting a refund before returning item

I sell books on amazon I list a flat price and out of that I pay for media mail shipping, a customer requested expedited shipping which I honestly didn’t catch but for me to pay extra for that would be customer would be getting book for free.

Because customer complained book would not arrive on time, I send her prepaid shipping label to return the book when she receives it.

I suspect if I refund her money she will just keep the book.

Is it worth it or should I just refund her and chalk it up to a Karen tax?

Now Amazon says I’m