Refund is causing me to pay out of pocket costs above what I received

Description

I sold an item on ebay and stupidly underestimated the shipping by about $150!!! My fault completely. I contacted the buyer, explained the situation and she was happy to receive a refund. However, when I went to refund her money through PayPal, it is charging me $20.91 in sales tax and $8.26 in PayPal fees out of pocket. The total amount was $274.41 but I only received $245.24 after sales tax and PayPal fees. Can anyone advise me on whether or not I am responsible to now pay $29.17 out of pocket for issuing this refund?