You mentioned Exchange, so I would assume that you have Active Directory as well. Given that assumption, woolnoir's and Cluskitt's comments are muddying the waters unnecessarily (no offense, guys, but it's true).
Everything jorlando66 said is accurate and relevant, and exactly what you need. If you go into ADUC on the server and right-click -> rename on the user, you can change the name as needed and it will have NO effect on the user profile on the workstation; the change will be entirely cosmetic. You can even change the username she uses to log in; she'll need to log in using the newly changed username, of course, but it still won't affect the profile.
(I can confirm all of this from personal experience; I've done exactly this kind of name change, for the same reason, many times.)
:)
