I'm afraid the first part is not clear in meaning. If what I have written below is not what you meant ask again.
This time Wendy didn't ship the goods to the wrong destination,
but she did provide the forwarder with incorrect details of the consignee,
and so we need to provide them with a letter for this revision.
It seems she is quite prone to making careless mistakes when preparing shipment documentation and is obviously not aware of the seriousness of this. I will talk with her later and
try to monitor her work more closely with the aim of preventing further errors.