Familiar by Nic Silver
Series: The Others, Book 3.
Approx. 79,940 words.
Published on October 1, 2013 by
White Raven Press.
To save Evgeny, Su had to allow herself to be bound to her hexen best friend Alex as a witch's familiar. They meant to reverse the spell as soon as Ev was safe, but it turns out a familiar binding is for life -- or even beyond if the familiar is a hexenfuchs like Su.
As the binding draws tighter, like a leash around Su's throat, she and Alex travel to Germany to search for a solution.