Assuming she had downloads running non-stop during the 4 months, at a maximum of 7 mbps (3g), she would have downloaded 8859 GB. With a $193000 bill, the "significant theft" was Telestra charging $22 per GB.
http://www.telstra.com.au/mobile/plans/phone_plan.html
They charge more like $2/MB. Sadly, Australia absolutely sucks in terms of internet access costs.
(7,000,000/8) = 875,000 bytes/s = 0.834 MB/s
0.834 * 60 * 60 * 24 = 72,057 MB/day
(EDIT: Tweaked numbers, had mistyped 0.834 as 0.844 — doesn't affect the point)
http://www.telstra.com.au/mobile/plans/phone_plan.html
They charge more like $2/MB. Sadly, Australia absolutely sucks in terms of internet access costs.