Flairfur resulted to cannibalism because her clan went through a particularily harsh leafbare, and couldn't stop. It escalated to the point where, in the following greenleaf, after killing a cat in a skirmish over borders she started eating him then and their. Disgusted and horified her clanmates killed her. After entering the Darkforest she realized how disgusting she had become and vowed not to eat another cat(whether or not she kept it...)