Oh, and to best take advantage of the promo Christian freebies, I suggest you encourage your sister to set up an Adobe ID and Reader/Kobo store accounts, if she hasn't already.
You don't need any of their devices or even CC# info to secure the freebies at those stores (NB: at Kobo you have to click the "Add to Library" link under the cover to keep the free books in your account for later re-download), and in my experience, they tend to only last about a week or so.
A couple of days ago I made a
round-up of all the currently available recent Sony promo freebies, and there's a good selection of Christian fiction (about a dozen titles, some holiday-themed) in the lot.
If she moves fast, she can get stocked up on her reading list even before she has the 505 to read upon.