Lady Alexine is described as a slender woman with long raven hair and almond-shaped eyes.
Lady Alexine is a Phaser, which means that she can walk through solid objects such as walls. In Book 1, she walks through a wall to yell at Dex and Stina after Stina put a muskog in Dex's locker. Sophie is a little frightened after seeing this, because it is her first day at Foxfire and she has never seen a phaser before.
Sophie had to use telekinesis and was doing well until Lady Alexine ran through the wall, breaking her concentration. Lady Alexine does this to make sure that her students can hold concentration and use energy.