I had a kindle that my wife used so often I have bought her a new one for Xmas. I also bought a few books to go with it but I have bought for my account?with out thinking .The old kindle has not been turned on since I made the purchases so they won't no it. Can they be sent to her account/kindle or will she need to read them on my one.
Use the same account on both Kindles
You can have more than one device on one account so she should be able to download all the existing content and any new stuff to the new kindle. Just use the same account details.
You could use calibre to load the books onto the kindle. It's quite a handy peice of software anyway for converting from other formats and just backing up your e-book library.
http://calibre-ebook.com/download
Yes everything is interchangeable when you log in with your user you will have both hers and your books in your carousel