Vixen

The Vixen was a female demon who associated with the eldest Thunder Brother, Hiten. Hiten thought that she was very beautiful and kept her for company. However, he did not value her life and killed her with a lightning blast after getting angry at his brother, Manten.

Anime vs. Manga
In the Anime, she's electrocuted to death by Hiten after he finds out that Manten hadn't obtained the Shikon no Tama shard from Shippō. In the manga, Hiten killed her by punching her through the head.

Zorra Demonio Dimoni Guilla 狐狸精