Add alias address to default GAL in exchange 2007 sp3

I have a user that is using the email addresses property in order to receive email going to the email address setup with her maiden name. The problem is, the large organization still has people emailing the old address using GAL (global address list) from outlook. It's very odd, but within GAL, the old old name is either showing up as the active directory user name, rather than the alias email address, or on some users' outlook, not at all.

Is there a way to manually add an email address and user name for the purpose of supporting aliases?

(quick example, if necessary, Sarah Connor becomes Sarah O'reilley, so now her email address sarah.connor@sky.net becomes an alias, and the main email addres becomes sarah.oreilley@sky.net. But people want to see Sarah Connor appear from GAL when they do a search in the address book within outlook, not just Sarah O'reilley).