Albireo who is like the troll king of Negima calls her Kitty which drives her absolutely nuts for some reason. It's probably a diminutive of Katherine, which is the 'K' in 'Evangeline A. K. McDowell.'

Like I said my personal theory is that she gave the nickname to herself back when she was a Tolstoy fangirl - it's canon that she really likes Anna Karenina - and is now horribly embarrassed that she did so.