I don't think that particular router support remote management, you should double check. You can use another technique by installing a remote control sever on your mother's laptop and have your computer control her laptop to access the router configuration.
Have a look here
http://www.tightvnc.com/
You install the server (host) on her laptop, making sure you disable or configured her firewall or security applications like anti-virus to allow port 5900 and 5800. Then you configured her router to forward port 5900 and 5800 to her internal IP address that she got from her router (usually something like 192.168.1.100 with Linksys routers). To find out her IP, just open up command prompt on her laptop and type ipconfig /all
After you are done configuring her operating system and router, you have to be on her laptop and go to
http://whatismyipaddress.com/ to get the external IP address (usually this is the IP that the ISP assigns to her modem).
Make sure you configured the TightVNC correctly on her laptop and create a password for security reasons.
On your computer from a remote location, you'll install the client (viewer) on your machine, and using her external IP address you'll connect to it and the rest should be pretty obvious. You have control over her laptop.
There is a documentation on their site that will help you get started. I wouldn't recommend TightVNC over the Internet because the only thing encrypted is the authentication and the rest of the packets are not, so to speed up the transfer. if you need real security, I recommend installing OpenSSH, and using SSH tunneling for all TightVNC connections from untrusted networks. But this type of method is slower and depending on how fast her upload speeds are it's probably going to be unbearable.