Hi, there is no 'standard' way to filter 'problem' traffic. However, if the problem is the AMOUNT of traffic, then just a small sample might suffice. Ask your friend to do nothing specific on her computer(s) and collect network traffic for a few minutes. Analyse the data manually to see what is the type, the source, and the destination of the most of the data captured.
How much is the data cap? Divide that by 30 (days) times 24 (hours) times 60 (minutes) and you know how much per minute that is. Does the size of the capture per minute amount to more than this limit?
Anneb