Tara

"You have to be Tara," the new Willow said. "After all the whole point of this, is that Willow can't live without Tara."

The witch quickly grabbed her lover and cast a spell. The original Willow's body filled out, her hair changed to blonde, soon she was physically Tara McClay, then Tara's memories flowed into her, then Tara switched their souls. She was now Willow Rosenberg in all things, just as Willow was now Tara. She took the charm that had transformed her and through it around the other witch's neck while making a minor change in the spell.

"Well that was complicated but it acheived my goal. And since I don't make the same mistakes twice the alteration in the spell will insure you don't want to become me again."

Willow looked at Tara who was gazing at her with adoration and worship. "You have a lot to apoligize for."