Is this on BES? You didn't really specify. I'd guess yes from the context of your message but it would help to have all info for proper troubleshooting.
Originally Posted by Paolo264
Also, if she tries to create a new appointment on the BB and add attendeexxx8217;s, she is brought to the BB Address Book but she cannot select any attendeexxx8217;s to add - instead, she sees their address book entry.
So it's not performing a GAL lookup? Are you sure that her Enterprise Activation (again, assuming this is a BES environment) is completing properly?
Is she using BIS at all?