Is it possible that her laptop is out of space. There is space necessary on a copy to a LAN drive to hold the files temporarily, until write confirmation is achieved, kind of like a cache. Perhaps her hard drive does not have enough space to hold the temporary files, until write can be confirmed across the LAN.
Just a thought. I have copied several gigabytes of mp3's from a laptop to the core, but I had at least twice as much free space on the source hard drive.