Wierd. I want to suggest that either:
1) The printer driver chosen is not correct.
2) The "print processor" used by Windows is not correct.
3) There is some sort of "header" being added to the printer's output by Windows' print queue.
4) Possibly, there is some sort of hardware-level communications problems with the printer, and commands that are supposed to be processed internal to the printer, are being recieved and displayed as text? (This is also what could happen when using the wrong "print processor".)
The easiest solution that I can see, is to un-install the printer drivers completely, and then re-install the newest ones from the mfg, and see if the problem persists. If it does, see if the drivers have any sort of "printer communications diagnostics" tool, and run that. If you are having hardware problems due to a poor-quality printer cable, that could be it.
Btw, are you using USB or parallel? Depending on the computer and the USB chipset that it has, that could also cause issues. Older Via chipsets are known to have USB problems.
Does that wierd string, appear exactly the same way, on all output, from different programs? Or is the wierd string different every time, or is she printing from the same program all of the time?