This is not a cover, guys! "Crazy" is a ballad composed by Willie Nelson. It has been recorded by several artists, most notably by Patsy Cline, whose version was a #2 country hit in 1962. Partly due to the genre-blending nature of the song, it has been covered by dozens of artists in several genres over the years; nevertheless, the song remains inextricably linked with Cline. Nelson's own version appears on his 1962 debut album ...And Then I Wrote.
I got the duet version too. It took me forever, but I finally found who she is! The version I'm hearing features Susan Tedeschi, a blues and soul musician...I had never heard of her before. It's a really good version though.