Genny is the Rolereverse version of Asriel.
Before her death, she was a docile, unadventurous and loving child. She cared for Gaster as a sibling, and she trusted him when he came up with a plan to escape the Underground that involved consuming buttercups.
In the True Pacifist ending, she is very apologetic towards Cameron.
As a wolf, he has grey fur to her shoulders and green eyes. She has visible fangs. She wears a red and blue striped sweater, shorts and no shoes.
In her "Goddess of Hyperdeath" form, her sclera's are black, her pupils are white and her fangs are longer. She wears a robe similar to her mothers and no shoes.
In her Angel of Death form, she body is more geometrical, she has crystalline wings, and her lower body has become sharp and heart-shaped.