If you haven't already done so I would suggest that you have another go at contacting eBay Customer Services and see if you can get through to somebody with an ounce of sense on the next attempt. Just because you got through to a total jobsworth the first time who behaved as though it was his/her job to be as awkward and obstructive as possible doesn't necessarily mean that you'd get through to a similar type of person the second time.
If you do decide to give it a shot and manage to get through to somebody who comes across as willing to listen to your query then explain in full exactly what you've said in your post about the buyer, then once you've drawn eBay's attention to the buyer's behaviour ask very firmly for the negative feedback to be removed, stating that the buyer clearly has a track record of doing this kind of thing. If you are lucky enough to get through to an eBay rep with an ounce of sense and he/she agrees with your reasons as to why the feedback should not be allowed to remain then you may well end up with the negative feedback being removed.
If you do decide to try again with eBay Customer Service make sure that you don't leave it too long, as if you run out of time you'll be stuck with that negative comment forever. If you just give up and do nothing about it then you definitely will be stuck with it forever, but if you stand your ground and fight to get it removed then you may well succeed if you're lucky enough to get through to a decent eBay rep who doesn't just act as though it's his/her job to be obstructive and unhelpful. If you do manage to get the negative comment removed then the associated defect will also be removed from your account, in which case the buyer's comments will have caused no lasting damage to your account.
Finally, if you have not already done so make sure that you add the buyer's User ID to your Blocked Bidders List so that she cannot purchase anything else from you in the future and cause you any further aggravation.
