The fact that it seems synchronized with the frames makes me think it could be a leaky light seal at the opening end, or even hinge end for that matter, of the camera back. Light is probably hitting the film either before or after the actual exposure film gate. Effects will vary depending on intensity, angle and duration of light hitting the critical area of the camera. She could experiment with putting black electrical tape (or gaffer's tape if available) over the joints where the back meets the body. Unless the camera was sitting a long time between exposures, I suspect the culprit seal(s) are bad enough it will be obvious just from inspection.
And that left frame in that first shot does in fact appear to have a fuzzy vertical bar all the way down the frame.
DaveT