If you test by sending an email from a pop account to the user then check the MAGT logs for that user at that time, should be at the bottom of the log. That might give you something to go on. Sounds strange if they don't have any rules enabled.
You can post the log lines here if you like, just remove the sensitive info first
Also, how many users are on the BES? How many have you tested with? If this is the only user then it has to be her account. Did you check rules/filters in OWA? Does the user have DTM installed? If so, check for rules/filters there as well.