Buyer hasn't received an item you shipped

[sellmystuff.2006]

Hi  I have sent a parcel to a buyer on May 11,2015 it was tracked, the problem is that the buyer hasnt received the item on time (19th May) and its been a week late on delivery. I contacted the Post office and they said that it was still in transit and they dont think it was lost. they didnt  give me more info since it was too early for me to file a complaint. They need it to be at least 10 days delayed before they can investigate.Now the buyer is getting frustrated and wants her money back. Should I issue her a refund or just wait until the Post office cantacted me again. I am a bit lost here since I have done the right thing and I have the receipt and the photo of the parcel before I sent it and even have a tracking #. Wanted to contact ebay but there's no category for this type of cases. Anyone please enlighten me?