Buffy the Vampire Slayer: Wicked Willow II - Shattered Twilight (Wicked Willow, #2)

Even Willow's own coven has turned against her now. Condemned for saving Buffy from their evil phantom and for not protecting the other coven members fully, as she had promised, Willow must come up with a way to restore herself to them -- and to reinforce her position of power, which hangs in the balance.
But the truth -- that she battled the phantom because the ghost of Tara told her to -- will only lower Willow's status in the eyes of her coven. It is time for big magic. Infallible magic.
And as Willow turns to the elements for protection, Buffy and the rest of the Scoobies must find a way to fight back without losing Willow forever....