I'm not sure what you mean when you say wi-fi for her cell service...do you mean she has 3g or 4g on her cell that she can serf the web? Most cell phones are capable of that, but you have to pay a fee for it. I do know some Kindles are 3g capable but you have to pay for the service, I do not know if the Nook is 3g capable. I am in the boonies too (no dsl, cable, or speed net...only thing available is satellite and dialup and the satellite is expensive and almost as slow as dial up), but I can get 3g on my cell which in turn I use as my internet on my desktops and laptops, I wirelessly tether via mobile hotspot (an app on my phone) and share my web allowance with my cell phone...so to do this, you would need a smart phone (with internet access 3g or 4g) that is capable of mobile hotspot or the box that Sara is talking about and you could connect wireless via your cell to your Nook (I am assuming the Nook has a wireless router like the kindle). That being said...you should also be able to use your dial up to download a book (again I am assuming the Nook is like the Kindle where you create an account with Barnes and Noble on any computer and can download books and plug your nook into your computer and transfer the books). I did used to download mp3 (songs) via dial up...it would take 15 mins for a 4 minute song but it would work. A book should not take as long as a song, so I would think it would be possible to download a book via dialup and then plug your Nook into your computer and transfer the book from computer to your Nook.
If you have a debit card you can purchase anything on the internet just like a credit card. I don't really like to use my debit on the internet though, but I have. One thing you can do if you are afraid to use your debit, is to purchase a Barnes and Noble card at Barnes and Noble (like a gift card) and use that instead, so you aren't putting your debit card out there on the web. Or even purchase a visa or mastercard gift card and use that to pay for your books (usually a $5 activation feee for those though). Most store specific gift cards do not have activation fees.
I hope all this makes sense, I am not tech savy either but living in the boonies I do know about tethering with my cell so I hoped I explained it well. Feel free to ask me any questions and I will do my best to answer them.
Congrats on your Nook!
