your poll actually highlights an issue I have about ereader devices in general. Outfitting a family of 4+ people is a mega-buck or more...even if you go with just a Sony solution @ $200/pop for the PRS500.
Four Kindles cost a total of $1600 w/o any content.
That said...buy her a Kindle AND subscription to a couple of her fav magazines or something...oh, and also give her a nice foot rub...or whatever else works for her...

If she does not like the Kindle, swap with her later.
Of course you could add a copy of the Kama Sutra to the Kindle for her reading, ahem, pleasure...