No easy way, it was available for only a limited time, and the server that had it is long since gone.
The only way to get to connect is to hack the data on the sandisk. This varies by sub-model (no outward sign of what sub-model you have), with a range of difficulty between hitting a few keys at the right time, to having to reflash the bios, boot Linux off a laptop harddisk using a modified cable, and dd'ing an image to the san disk. See threads on getting an I-Opener to use another ISP which, even though you're using the ISP it was made for, you still need to do the modifications, as Earthlink no longer has support for an I-Opener.
You might cosnider picking her up another internet appliance. Most of the older ones are fairly cheap now, and some should fit your grandmother's needs without needing to be modified.