How do you force Exchange to permanently delete "Deleted Items"?

I have a user that recently exceeded her mailbox quota (200MB).  She went through and deleted a ton of emails, a bunch of sent emails, lots of large attachments, etc.  After doing so, she also emptied out her Recycle Bin in Outlook.  Now, when she views the mailbox size in Outlook, it shows that the "Local Data" is roughly 35MB (well under the quota)...but that the "Server Data" is still over 200MB.  She deleted all of these emails two days ago, yet the information on the server has never updated.  I've tried running the Exchange "Cleanup Agent" thinking that might fix the discrepancy...but no such luck.

How do you force Exchange to permanently delete "Deleted Items"  for one particular mailbox (and only this one time)?  Thanks in advance.