"Disappearing emails" is occasionally reported but there seems to be no
single obvious reason for it. broadly speaking, version A of Word does not
tend to work too well with version B of Outlook, but from what you say, the
upgrade to OL2003 was probably a response to this problem rather than the
cause of it. Is that the case?

Some things to try:
a. Check Outlook Tools|Options|Other|"Advanced options"|"Enable mail
logging (troubleshooting)".  Then restart.
b. if you have a COM Addin called bxAutoZip (see Outlook
Tools|Options|Other|"Advanced Options"|"COM Addins") disable it temporarily.
(If you have other addins and disabling them will do no harm, I'd do that
too).
c. make sure you know where your .pst file is, make a backup copy, and run
the SCANPST.EXE utility - on my system it's in

C:\Program Files\Common Files\System\MSMAPI\1033 )
d. recreate your Outlook profile (I don't have a good set of instructions
for that right now)

Some questions:
e. could this problem be related to a specific update? (i.e. can some one
look and say it worked before such-and-such a date, and after the update
recorded in Control Panel|Add or Remove Programs| it stopped working
f. is Outlook the default Mail program (IE Tools|Internet Options|programs)
?
g. what kind of merge is she doing (HTML, plain text, attachment)?

Peter Jamieson