The castle had originally intended something else for Sarah, but that was now out the window, it couldn't change what it had already transformed. But still, with each person it changed, the more its influence grew and the more people it could draw to the castle, the night would last as long as it needed to restore the inhabitants of the castle.
Still, the haunted castle did, ever so slightly try to match up its victims with some basic traits they had with what it needed.
The castle wasn't about to do something as baneful as ASK PERMISSION, such a thing was beyond taboo, and outright dishonorable, how could it claim to be a terrifying and haunted castle, if it did something like ASK someone if they wanted to be changed. Such behavior was completely unacceptable.
As a most basic nature and rule of the castle, unlike werebeasts people knew about in movies, these werebeasts did not assume a human form, the alpha only had the full beast shape they could change into and out of, that was normally several times larger than the normal size of the animal, and and the rest only had their anthro shape. They would never appear human again. This was a basic nature of the castle's changes and couldn't be changed. Anymore than the castle could 'undo' what it had already done.
The castle's witch had one wrestled control of the castle from the cute and adorable vampire lass who had lorded over this castle in its beginnings, but in the end, the vampire lass was staked, and the witch burned, leaving the castle without its true or surrogate master. But it would find a successor soon enough. It knew a basic truth about humans, children were in reality the most vicious of monsters, they hadn't learned social mores, or empathy yet, and the best to make monsters FROM.
But it was now short one monster, but it would make due, after it had completely changed this lot, it would draw in more to change to fill the void.
It could try to change Nate into the witch instead of Sarah, but while it had no problem with changing a victim's sex, Nate was simply too good a potential werewolf to let go.
So the rooms arranged them in a circular pattern, and Nate ran, with Sarah right behind him. Sarah's instincts screamed at her, and instincts were not some voice in your head you argued with, they were what you did because they were the most natural thing in the world. And so Sarah feel pain at Nate possibly rejecting her... realized she had the perfect gift to make it up to him, and the perfect way to make sure he stayed her forever.
With newfound purpose and drive, the great wolf howled and bounded after Nate. Nate called for help of course, but the castle make sure the others didn't hear him. The great wolf that was once Sarah leaped and tackled Nate to the ground, biting him in the hand as he squirmed under her superior weight.
The brown and silver fur spread over Nate's body even as Sarah ripped his clothes off, leaving him naked, but it didn't matter for long, and in a few moment, Nate didn't care or even thinking about it. The tail grew from his behind as his feet became digigrated, and his claws formed on his hands and feet, and the callow on his hands and feet. He hunched over as his face became a fang filled muzzle, his ears pointed and to the top of his head. He snorted and growled and Sarah finally let him go. His muscles bulged and his eyes became crimson. He howled, and she howled back.
She shifted and formed back into her humanoid shape. The two werewolves sniffed each other, and without a word, understanding each other's without needing them, they embraced and hurried to the empty and barren garden inside the castle, ready to make passionate love under the moonlight, their friends forgotten about.