Kwannon's body-switch with Betsy Braddock occured behind the scenes in Uncanny X-Men (1st series) #256. She first encountered her mirror-sister in X-Men (2nd series) #20. Her Legacy infection was revealed in X-Men Annual (2nd series) #2. Kwannon was mercy-killed by Matsu'o in X-Men (2nd series) #31.
After an encounter with Sapphire Styx in Death of Wolverine: Mystery in Madripoor #1-4, Betsy Braddock's Asian body died and was replaced by her original British body. As a side-effect, Kwannon seems to have somehow been resurrected in her original form as well.