She bites you early on, in the feverish first days of your courtship. Through the change she mops your brow and makes comforting noises. You wake to fur, pin-sharp vision, new muscle bunching around limbs that are now hind legs rather than simply legs. The two of you run together through the woods and you are happier than ever you have been in your lurching human shape.
Time passes. The intensity of your love begins to fade. You drift apart, but you never stop being a wolf. Your next lover begs your to bite her, and so you do, and for a time the pair of your run together. In her you see your first. You will always see your first in every wolf you run with. She spreads through you and through your life like a virus. She is in your blood. She is in everything you ever share.