Actually, you don't need anything special. All you need is a computer which has speakers or headphones and you're good to go. Only aditional software you'll need is $1 and it's completely free.

In addition to NVDA, you should start her off right with Google Chrome and UBlock installed. Not all browsers are created equal when it comes to accessibility. You could also install Firefox as an alternative; UBlock is also available on this browser as well. Good uncles don't let nieces use Microsoft browsers. :) The ad blocker is important, as most ads are even more intrusive when you're blind. Save her the pain of dealing with that. Forget about Adblock plus or things like that as they sold out and will not block ads from certain ad networks.

Does she know how to use a computer? If not maybe NVDA isn't the best starting screen reader. Blind people use computers completely different than sighted people, and terminology is different too. Have you ever heard of this thing called a combo box? Sounds embarrassing, I know, but we have to hear these weird terms all the time. Also, radio buttons, check boxes, and dialog boxes. And panes, plenty of pane.

Do you mean tutorials for how to build? There are a couple places you can check out.

r/pcmasterrace has a lot of good general PC information.

r/buildaPC is specifically dedicated to building computers.

Pcpartpicker.com will let you browse hardware and create a rig with compatibility filters so everything works together. You can share the build with other people and view builds that other people have made which have been optimized for various things like budget or power or productivity.

Linustechtips on YouTube also has a ton of tech stuff and they have a few PC building tutorials. YouTube in general is a great place to find tutorials on how to put a computer together. You have sight so this should be pretty easy. It's mostly just plugging in cables and cards into sockets and hey, you might enjoy it and turn it into a hobby :)

Just don't cheap out on the power supply. Never buy a cheap power supply. Oh, and don't forget to add peripherals like a keyboard and speakers into the budget. Also a Windows license, you know since not paying for it is illegal or whatever. Last thing is to make sure to get a full size keyboard with a numpad. It's pretty handy and pretty necessary for a screen reader like nvda.