There isn't some "Disconnect if idle for more than ( ) minutes" option set up on her machine, I suppose?
Were some spotty little geek to 'crack' MAC address limited access to a wireless router, would his MAC show up in the 'client list'?
I only have 3 addresses permitted to access my router - 2 laptops and a Canon i5200R printer. If a geek got in, would I know?