This is no surprise to me as a descendant to Viking heritage I know that there were many women warriors who fought along side the male warriors. This is what made vikings so fierce. They would battle each other as much as the battled others. To see a woman warrior grow in strength and power is not unheard of and many lead some great fleets to attack others.
I understand this too. Spartan society allowed women a tremendous amount of liberty. Spartan women trained in sports alongside men. This is usually the case in warrior societies. While the men were off fighting the women protected the home. In this case, this woman was off fighting too, and actually leading men.