The only thing I can think of is that it's related to her iPad's Restrictions, as Machinarium has a 12+ age recommendation. I suggest that you check that out to make sure that Restrictions are set to Off. If you're not sure how to do so, you can access Restrictions under Settings > General > Restrictions > Apps.
Here's a link to an Apple Support page that has images and more details:
http://support.apple.com/kb/HT4213?viewlocale=en_US&locale=en_USAlso, you might try going to Settings > iTunes & App Store, tapping your Apple ID, signing out, then signing back in to see if that makes any difference.