Well, don't know if she has a router, but I suppose you could change the port settings to work only during certain times of the day......... (don't know what port MSN runs on.... since I don't use it, but I'm sure it's easy to find). Most routers have a way to restrict by ip and port the time of day that they are open.
IE: Easy for an administrator at say a place of business, that knows no one is using the computers after 5, to shut the ports off, to help ward off hackers.
Thats the easiest way I can think of anyhow. Hope that helps.