The only way I know to do this is with a CradlePoint router with the Verizon USB adapter plugged directly into the router.
All you need to do is enable the Hotspot feature on your Aunts iPhone and hook it up to a wireless repeater. That way all devices will be connected and able to communicate with each other.
iPhone ))))))) Repeater )))))) Printer
iPhone ))))))) Repeater )))))) Computer
)))) = Wireless signal
With this kind of setup your computer and printer are always connected to the repeater. When the iPhone is within range the printer and computer will have internet access too. When the iPhone travels out of range/powerd off then they will only have LAN access.
There are many products out there that will perform the repeater features that you need automatically. I personally use a device called the Pepwave Surf and it works great. However you can purchase similar devices from Netgear, CradlePoint and a few others as Jim suggested.