Negative feedback received because buyer subsequently received same item for free.

[peppertreebuys]

Hi, I'm a newbie seller and received my first negative feedback. I sold an item for $2.00 then received an email a few weeks later from buyer saying that she recently received the same item for free so thought it was unfair that I sold something she could get for free.  I told her that it was irrelevant how much I paid for the item however if she was unhappy I would refund the item once she returned it to me.  She basically said no to returning the item, but still wanted a refund or she would leave me 'appropriate' feedback.  I again gave her the option to return for a refund and she refused, so she has now left me negative feedback.  Is this something that I could ask eBay to withdraw her feedback on or should I just respond to her comments?  Thanks for any suggestions.