CS, I would not get a kindle fire, if its about reading no need.
Get her a Kindle Paperwhite 3G. Check the size though on the pictures at amazon.
http://www.amazon.co.uk/gp/product/B...684634-2937953
It is not huge, get a cover for it too, and get a charger. Sold seperately both.
With the 3G version she does not even need internet. It is all included, usage of 3G is too, you do not need a card! It works WORLDWIDE, price of using amazon's "whispernet" (basically a deal amazon has with AT&T for worldwide 3G roaming just to download data) is included in book prices.
And it is quite simple to use too, you buy the books right on the device. You can also buy them on any pc logged into your account linked to the device and it automatically get pushed onto the kindle.