How can I get this incomplete MOV file to work?

That's an awesome story to explain to your girlfriend when she asks what happened to her camera, but nope no judging here. The issue may very well be the incomplete file transfer, but if it showing up in your computer folder as a complete file then you might have something left to salvage. Make sure that the computer is using the correct codecs (basic drivers to run A/V tracks) and that it can open other files from the camera with no issues. If it is opening other files well enough then you know that there is a file corruption error. Attempt to run a disk check on the SD card chkdsk (SD):\, and otherwise there are probably hundred dollar programs out there to salvage digital media files. I would just be glad you didn't lose the SD disk too.