She will need to plug the PC into the router by wire just to setup the wireless when done it can be removed and used wirelessly. Is it cable or the old Virgin.net ADSL? Also what is the Model of the router?
In that case it is quite straight forward connect by wire to router and router to modem then run the setup CD that came with the router and follow instructions once setup remove wire and use wirelessly. Please setup security as well WPA2 if can if not WPA.