Here's one possible solution which I used to resolve a similar problem. YMMV

Are you using Simple File Sharing (the XP default)? In Windows Explorer, select Tools, Folder Options, View and uncheck "use simple file sharing..." at the bottom of the Advanced area.

You'll then need to grant new user or group shares for everyone in the workgroup to not break their access (or at least I did when I made a similar change).

Either create a traditional "guest" userid and password, or create individual userids on your computer that match all the userids on the computers in your workgroup and one for your girlfriend. Being a paranoid computer type, I'm all for the latter option.

If you chose the latter option, create a "sharing" group, and add all the workgroup userids and your girlfriend's new userid. Using the latter method, you can also share specific resources on a userid by userid basis, as needed.

Share the resources with the guest id or the group (depending on which way you went), granting whatever rights you want them to have (I think "full control" is the default for simple file sharing).

It should prompt her for her userid on connecting. If you use the same userid as her work userid, she may have to name herself as "workgroupname\userid" rather than just "userid".

-jk