Make her howl with pleasure.

You wonder how you could possibly deny Amy this gift, this power? You will share this wonder with her, and make sure she is completed.
Amy gasps beneath you, and you can feel her vagina beginning to clench around your tongue. Without wasting another second, you clamp down on her thigh, piercing her skin with your fangs and contaminating her blood with your infectious saliva. She screams in pain, maybe pleasure, and continues writhing as her orgasm comes seconds later.
You know what will happen now, and you want to witness her lycanthropic rebirth. Deftly, you spin away from her face, hunkering down on all fours before her dripping snatch. You watch her intently as you bury your tongue inside her slit.
Amy thrashes in pure pleasure, from your tongue and the moonlight awakening the wolf you have placed within her body and soul. She screams, almost a growl, and digs her nails into the carpet. As she draws them forward, you hear fibers ripping; she is growing her claws.
She presses her crotch against your muzzle, quickly burying itself in a mesh of thick black pubic fur, and snarls at you to continue. She had the slightest hint of fangs in her mouth and the barest of points to her ears; her eyebrows have grown together in a large bushy mass, over eyes that are completely lupine.
You oblige your transforming sister, and go down on her with fervor. Everywhere she changes, from her rising ankles to her inflating teats, your paws instinctively grope. She screams, then growls, then howls with rapid-fire climaxes.
After her fourth climax, once her tail fully extends and her muzzle finishes its growth, she flips you over in a burst of her newfound lycanthropic strength. You clamp your open muzzle around her bestial crotch, tongue-fucking her to a howling ecstasy.
She dismounts you soon afterward, a full werewolf. It saddens you that she cannot be your mate, that no one can. She, however, has the right to be properly mated, and as her creator and fellow werewolf, it is your duty to find her a suitable partner.
The pair of you rise to your paw feet, and tear away the front door of her apartment with massive strength. Your senses tell you both that there are still others in the complex; you also hear sirens in the distance.
You must decide your action quickly!