If I recall when third party apps use the locations services that data being stores drops off when it is no longer in use. Plus it uses the apps area of storage for the buffering of locations services. Don't quote me but I am 92.6% sure.It's could be the Location Services that is eating up addition data from third-party apps. Apple does this as well with System Services within Location Services in the Settings app.
When she has her phone plugged into iTunes it wouldn't be showing that location services data in the other area.Your probably right but the person your trying to help maybe has her location services on so data could be accumulating undesired amount of data?