Outlook XP other user’s Inbox problem

I have a lady who can view her manager’s Inbox, with permissions set as Reviewer – she can read the messages, but nothing else. However, when she looks at the list of messages, each message is marked as read when she moves to the next. (She is not opening the messages, just moving down the list one by one). She then has to mark them all as unread for the benefit of the recipient.

This does not happen in her own Inbox.

I have looked all over, including MS Knowledge Base, but no luck so far. Has anybody come across this before, and if so, can it be fixed, or will she have to live with it?

Thanks in advance.

David