Judges 4, part 3: Yael, deceiver and piercer of the serpent

Yael, the lady of a house in league with the Canaanite king, defies her husband by deceiving and slaying Sisera, the principal of the Canaanite army. What should we make of Yael’s treatment of Sisera? Is she a liar and a murderer? Or is she indeed blessed among women? And if so, what is the implication for women in the church, and spiritual warfare?