Many routers now will allow her to plug in a large hard drive to the router using USB, making that storage available to the network.
Leo says an 802.11n router would be good. If she has DSL now, she probably has a router already, but the question is does she have a Wi-Fi enabled one? Usually the router that comes with broadband is pretty basic. Leo says that Wi-Fi routers are a commodity now and there's not much difference from one to the other. That being said, Leo likes D-Link and NetGear. He's not so fond of Linksys. If money is no option, the Apple Aiport Extreme is the best.