Hmm... My guesses are:

1. are other emails from people on your friends mail domain coming through? do you have your outlook configured to remove the emails from the AT&T servers immediately? if so, are all other mails pulled from the server and only her mails remain? that sounds pretty odd!

2. what have you configured your rule to do? move it somewhere? mark it as read? make sure

3. if it's marked as [bulk] are you sure this is something that Outlook is doing? or is that something AT&T is doing? (does [bulk] show up in the subject line when it's sitting in your AT&T inbox)?

What addressbook are you referring to? Outlook generally uses the contacts list for getting email addresses...