Yes, definitely worth it, and quite easy.
However, if she has a wifi card, and you have a wifi card, you don't need the router. It takes two seconds to set it up as an "ad hoc" network, meaning the two machines communicate with one another as peers. So one of you has the DSL or cable modem or whatever, and the other connects via wifi and pinches it.
I got three Wireless B (the old tech) cards on woot.com for $10 (if you're not checking woot every morning, you oughta). Popped one in my laptop and one in his at Christmas, and voila! We had a functioning network. Okay, it took fiddling with a few settings and a couple of reboots, but it was very slick! We didn't fight over the connect for the holidays.