it sounds like she just popped in her new ATT sim card without re-flashing the phone's firmware or doing a hard reset, which would ultimately prompt the settings wizard to run upon any new sim card being placed in the phone, which would pull all the correct att settings for data, text, etc.
so just run the wizard manually, and advise her to use ATT Internet access point for all of her data use. media net is only useful for going to the media net portal site.