I live in a retirement home in rural Arkansas. It's a HUD subsidised place so the residents are both old and poor and mostly technophobic. I've helped a number of them get started with Kindles and offhand I'd say 80% of them take to them pretty well. I've been doing this since about 2009 so not all of the Kindles have been Paperwhites. The Paperwhite is easier for them though.
The 20% who don't get comfortable with it, without exception, are the ones who are so afraid of it they won't really try. Usually I'll loan them a Kindle and show them how to use it and then check back to see if I can help a day or two later. The ones who try 2 or 3 times get it. The ones who don't get it usually just pick it up and look at it a time or two and are afraid to even turn it on. I usually know 5 minutes into explaining it to them which those will be.
Anyway that may help you decide about your mother. If she'll try it she can do it. If she won't, and some just won't, that's that.
The former manager of this place, who just recently retired, is 82. She wanted a Paperwhite and I helped her get it and I've probably spent 30 minutes about once a month with her and that's the only time she ever picks it up. She always has some reason. She's yet to read her first page. She's had it for about 2 or 3 years now. I think she just enjoys having me show her how to use it.
Barry