Just checked my iphone. The stats were cleared on 5th January; since then i've downloaded 218mb and uploaded 26.5mb.
I have 2 hours every weekday on a train where i'm mostly on here or other websites. I regularly run other apps so would be very surprised if she was anywhere near to the limit. I just tested and opening 5 web pages used 1mb of download.
As above if you have wireless broadband at home you can configure the phone to connect to that when it's available, use that for downloading music or apps as it's completely independant of the contract limit on the phone. Some apps are quite large so it's possible that a couple of these downloaded over the 2G connection have pushed the usage up, once they are downloaded they only use a small amount when in use. As an example the Michel Roux dining app is 293mb to download.
There are apps that will find free wireless spots when you are out and about, all McDonalsds have free wi-fi for example.
cheers
paul