Either right-click on My Computer on your machine or hers and select Manage. If you're on your machine, right-click Computer Management (Local) and select Connect to another computer ... and enter her computer address or name. Expand the Local Users and Groups section, click on Groups. Double-click on Power Users and click add. Either enter the username as domain\username or select your domain from the Look in drop down list and find her username.
Once they're in the local power users group, the user will have to log off and back on for the changes to take effect. Marc Creviere