If everything else is working on that network, then it's clear the laptop is the issue. It's possible that they're using a WPA2 password and the laptop doesn't support that. Since the laptop isn't that old, Leo doesn't think that's it. She is getting signal on the laptop, it's just not connecting to the internet. It could be Internet Explorer. Try another browser like Google Chrome or Firefox. It's also possible that the laptop is mis-configured for the new network. It may also be that malware is causing it, such as DNS Changer. If it's malware, it may be necessary to backup all data, format the drive, and reinstall Windows.
There is a way to find out if it's a connection issue or something else. She could go to command line (start, run, type "cmd" and hit enter). Then type "PING Yahoo.com." If it works, then the connection works. Unfortunately the best solution is to just have someone come to her house and look at it, because this is a very difficult problem to diagnose.