should automatically search for available wireless networks, and will offer them to her - all she has to do is tell the machine to connect to the network of her choice.
If she looks in the system tray (bottom right of her screen) she should see a network icon - it looks like two small monitors, one superimposed on the other. If she clicks on the icon a pop-up box will appear, with the option 'Connect to a network'. Clicking on this will produce a Windows network dialogue box, in which should appear all available networks.
Your daughter can then select her home network and tell Vista to connect to it.