Is it any better with WPA? Which you should use in preference to WEP anyway.
Alternatively, enable MAC filtering and secure the router's config with a decent password. Change the SSID to one of your own choosing to restrict identification of the router manufacturer.
To filter MACs, you'll need the physical address of the adapter in your wife's laptop; open a command prompt (Start > Run > command) and type ipconfig /all. Note the physical address and enter it into your router's MAC filtering option.
This prevents other wireless devices from using the network. The config password should prevent wardrivers from changing the situation, or at least make it extremely hard for them.
With so many unsecured home networks around, wardrivers pick the easy targets first.