I'm going to spend thousands on books over the rest of my life, and it's very frustrating that I won't be able to leave those to my family when I die. Unless I break the law to remove DRM.
Kindle is "smart" enough not to let the same book be read on multiple devices, which mimics physical books (you can't read a book that is not in your physical possession). Kindles are cheap, too. After about a dozen books or so you might actually save money even with a loaner Kindle.
I'm not disagreeing with you regarding the absurdity of ebook DRM, though. If you don't feel Kindles are ethically defensible, don't recommend them. If it's a convenience thing however, the two Kindle scheme might work for your mother.
Yes, a kindle is an expensive electronic device. The books are lent without any real expectation of getting them back, certainly without time limit. She receives from others, some books are returned, some passed on.
To effectively mimic that social pattern you would need one kindle per book, massively expensive (ebooks are seldom cheaper and the you have the device on top), environmentally unsound and just a really bad idea.
http://www.amazon.com/gp/help/customer/display.html?nodeId=2...
This is the major reason I can't recommend a kindle to my mother. She and her friends exchange books all the time, it's part of reading for her.