The reason she wasn't able to play it was probably because the game is relying on the RTP, which she doesn't have installed. RTP is the compilation of tilesets, sprites, background pictures, music, etc. that comes with the program. There are 2 ways I can think of for dealing with this (besides having her install RMVX):
1.) Have her download the RTP for VX. It would allow her to play any VX games without needing to buy the software. You can go to
this page, scroll down, and click on the link to "RPG MAKER VX RTP (35.0MB)" to download it. This is definitely the faster short-term solution.
2.) I know people do this for XP, but with VX I'm not 100% sure. But one thing you might try for the long run is to export and then import any of the RTP resources you're using in the game (so it recognizes them as your own imported resources as opposed to the RTP), and then turn off the use of RTP. I believe the way you do that is under Game->Select RTP->set everything to "None." (Remember, you'd want to do this only after you've exported all the resources you used and then imported them again) Also,
this link will take you to a thread someone wrote on this topic.
Hope this helps!