Heocwaeth (which means "she says" in Old English, for those who don't know the language) has a profile of Aethelflaed, Lady of Mercia that's worth a read.
As many of you know, I'm a real curmudgeon when it comes to medieval women writers -- I think too many are canonized because they are women (*cough* Julian of Norwich *cough*), not because they are particularly good like Christine de Pisan (who is, indisputably, super-awesome).
This isn't to say that I don't admire some women in the medieval world, and one of the most admirable is Aethelflaed. One of the interesting side effects of the West Saxon laws forbidding women from ruling is that all the royal daughters got married off to neighboring kingdoms were sometimes, like Aethelflaed, they blossomed into full power.
Aethelflaed, Lady of Mercia, Medieval Warrior Princess.