Boudica was a Celtic warrior queen who became a Valkyrie upon death.
History
In life, Boudica was a warrior queen of the Iceni tribe who lead revolts against the Romans until her death in 61 C.E., where she died in battle and became an Einherjar. Sometime later, she became a Valkyrie.
Magnus Chase and the Gods of Asgard
9 from the Nine Worlds
Just Another Decapitated Head
She is considered to replace Gunilla as captain of the Valkyries, however she cuts a lamp in two when she does not see snacks, which she was promised, and leaves. Odin passes on her for being too violent.