I am looking for a computer for my mother in law who is legally blind, do you have a computer that is voice activated or that caters to the visually impaired?

Windows and MacOS both have voice assisted operation that can be activated as well as other accessibility options to assist the visually impaired. Depending on what she is wanting to use it for....a voice assistant such as Google Home or Amazon Echo can be very helpful as well. I would definetly recommend going in and getting a demo

I bet they have software you can upload for any computer to assist

I don't think so. There's government programs that can assist