Run the [package command to gather the fonts and links, then export to .idml and add that to the package (so she'll have a file she acn open, in theory), and make a PDF and include it as well for refernce on what the documetn is SUPPOSED to look like, as the odds are pretty good isn't going to translate perfectly going back that far.
Package it. Close the file and then open the one in the package. File > Save as and change the type to InDesign CS4 or later (IDML).
You should probably send a PDF as well since the chances of a perfect conversion are close to zero. If that file is getting returned to you, you are in for a world of pain trying to work this way.
Thanks, will try this and hope for the best!