You sold a coat ($315) to an overseas buyer.
The buyer demanded a $6 partial refund on shipping.
You refused and shipped*.
She received the coat in Canada.
She sent the coat on to Hong Kong.
She claimed there was damage and demanded a 25% discount.
Or she would go to eBay.
Customer Service told you to file an extortion (Feedback Extortion?) case.
Which you did.
Although you Blocked the buyer, she could still send you Messages.
You were advised by Customer Service that you should escalate on Dec 26.
Apparently she had also filed a Not As Described case. What was the date on that and how did you respond to it?
On Dec 25, eBay reminded you that you had not responded to her Dispute.
Later on Dec 25, eBay closed her case in her favour, and refunded her the entire amount.
So what I see is that you were dealing with Customer Service, without realizing that the Not As Described dispute she had opened was much more important.
I would as soon as possible, contact Customer Service (although the Philippine office is probably the only one open they are now into Boxing Day) and appeal through them the Dispute.
Ask for a supervisor.
Show them the messages and CS discussion.
I'm glad you were dealing with CS through chat (?) and were able to capture the advice.
The blue highlights above are part of your appeal.
The coat was re-shipped after delivery in Canada. This normally will end the Money Back Guarantee.
And the threat -- although unless she mentioned feedback this is a weak defence.
*Hindsight is 20/20, but the best answer to this sort of demand is an offer to cancel the entire transaction, because, as you have learned, it will not get better.