This is mentioned in the new OHOTMU HC #13 entry for Yukon Jack. It says that she left Kemteron after their marriage ended under unrevealed circumstances, and Yukon Jack got sick from the time travel. From the way it's worded, it's amibiguous - his sickness might not have had anything to do with her leaving, or it was one of the causes. It's a poorly constructed sentence, anyway, I remembered you asked about this and was really hoping to see some new info on that!
Love,
rplass