1) Never send if you doubt the address even if they have paid, it is not unsual for some buyers to win and change their registered address even to keep it off of ebay, why I don't know, could be nervous could be fraudulent.
Many buyers are unverified and /or unconfirmed without being a problem that would only bother me if the item was very expensive and going international. in that case I would stipulate that in my listing.
Either way keep sending e-mails via ask buyer ONLY so it is kept on the system in case of dispute. Could be thier mail box is full.S ooner or later they must wonder where their win has got to.
2) First I would block her from bidding on anymore at least until this is resolved via your my eBay.
Then talk it through all by mail through ebay ONLY as above, if that fails file an unpaid dispute and then only communicate through the dispute console, is important to keep all communications on record in case of escalation.
In these circumstances it is not worth communicating by phone, letter or direct e-mail as it cannt be verified.
Be aware there are strict time limits on starting an unpaid dispute, and completing it.
Good luck and get back here if you need further advice from anyone.
P.S. mutual withdrawal means you lose all the fees and the buyer walks away clean, go through with the dispute she gets a slapped wrist of an unpaid strike, you get your FVF fee refunded, she may red you but that in my book deserves one in return. As a seller only give feedback after receiving it to avoid malicious or lazy buyers.