re: Can you transfer a Kindle book to someone else's account?

Or you can download the book from your Kindle and use a program called Calibre and then email it straight to her account.

Link to Calibre

I use this all the time with ebooks that I've downloaded. Its not hard to get setup and running.

You will need to go into your Device list on Amazon and find the address for your wife's kindle. Just follow some of the setup guides. If you need help let me know.