Both the Christian and Muslim ethos on war during the Crusades would not have sanctioned a strictly combat role for women. Some Muslim accounts of the crusades in the East make the claim that Christian women sometimes went into combat as soldiers, but these accounts are highly suspect as such an attribution would have shamed their enemies. Also, no Christian account of the time makes the specific claim of Christian women taking part in offensive combat. For example, while Guibert of Nogent recorded a "troop of Amazons" accompanied Emperor Conrad to Syria, there is no account of their exploits on the battlefield. If such combat did occur, it is likely to have been omitted in light of the potential shame this might have brought on crusader armies.
A careful review of the Christian attitude towards women during the crusades demonstates the general Christian concern of the sinful effects of having women present on a crusade in any capacity. This often resulted in occasions of their dismissal from a crusade [those women who served as washer women, cooks, prostitutes, etc..] and ultimately their attempted prohibition from participating in a crusade in any matter.
Aside from an occasional abberation, not usually endorsed by crusades authorities, or an exceptional situation requiring all hands for defense, the sources do not conclusively show that women fought in the crusades to the East. Yet if we examine the broader crusading movement, such as the Italian Crusades, the Reconquista, or the Hussite Crusades, such examples of women in combat, although still rare, are more common.
A few examples of major exceptions include Joan of Arc [Who threatened to lead a crusader army against the Hussites], Countess Alrude of Bertinoro [Led her army to break a siege at Alcona in 1172], Countess Matilda of Tuscany [Italian Crusades], and Duchess Gaita of Lombardy [Italian Crusades].
Many other women participated in warfare during the 11th, 12th and 13th centuries in places like Spain and Italy. I have not included them in this brief study only because usually such combat was not in the context of a crusade, instead often involving the supression of a rebellion in their realm.
"Among the Franks there were indeed women who rode into battle with cuirasses and helmets, dressed in men's clothes; who rode out into the thick of the fray and acted like brave men although they were but tender women, maintaining that all this was an act of piety, thinking to gain heavenly rewards by it, and making it their way of life. Praise be to him who led them into such error and out of the paths of wisdom! On the day of battle more than one woman rode out with them like a knight and
showed (masculine) endurance in spite of the weakness (of her sex); clothed only in a coat of mail they were not recognized as women until they had been stripped of their arms. Some of them were discovered and sold as slaves."