re: Does LTE internet drain your usage very quickly?

I need to see if there is a way to see what apps are eating data usage on my wife's iPhone 5. We are on an unlimited data plan so it hasn't concerned me too much, but we use Wifi equally, and her data usage is generally 3 times as much as mine on my 4s. It may have something to do with settings or a particular app. I never bothered to look because she's glued to the phone all day.