Okay...you originally said she couldn't connect to the wireless router (after saying that she could), but now you say that she can't connect to the internet. That makes more sense. 🙂
I'm not an expert in diagnosing these things, but I've found that DNS issues are often the source of things like this. Go to System Preferences --> Network, then choose AirPort from the "Show:" drop-down menu. Then click on the TCP/IP subpane. Does she have stuff listed in the "DNS Servers" field? If yes, make a note of the addresses (in case you need to put them back later), and then try deleting them. See if that allows her to connect to the internet.
If that doesn't work, I'll have to leave further troubleshooting to someone else. 😀