You may have to change the 3-letter extension...?
How can she import my Mac file into her PC PPT?
I am not sure if this helps, but PCs need a 3-digit extension to tell what kind of file it is.
You could try renaming the file on the PC
nameofpresentation.ppt so that Windows knows to treat it as a PowerPoint file. If you don't see 3-letter extensions (.doc, .exe, .xls, .ppt) on the PC, you need to change a setting show that the PC shows you those.
In a Windows window (like My Computer, or My Documents) go to:
View-> Folder Options
Click on the View tab, I think it is the second one over
Look down the list to the choice that says (o) Hide extensions for known file types and click on the button to turn that off
Click on Apply and close
That should show the 3-letter extensions to files, and you can see that your presentation does actually have .ppt on the end, and is not actually something like .ppt.mov, which the PC won't know what to do with.
I may have to go back and edit this, I am not a PC at the moment and need to check the exact path to change this setting.
Good luck.....!