Very few people connect directly to the Internet using WiFi.
Usually they connect by WiFi to their DSL modem/router and then to the net. So the speed to the router might be 54mbs but after that it might be 1mbs or 2mbs.
So, what speed is the modem/router she's using? That's the speed she'd be getting, not 54mbs.
It sounds to me that the 6mbs Internet is worth having.