Here are chord charts for some of Katie's songs. These are aimed at novice/intermediate players and so most of the versions are simplified so you can quickly learn to play the song. If you are of a higher standard you may be able to listen to Katie's versions and work out exactly how she plays them, or you can search on one of the many online guitar sites for a more complicated arrangement. And if you're pro standard then you can just buy the sheet music 😉
If you're learning guitar you should check out --> justinguitar.com
More on the way...neverending work in progress!