Female Warriors of the Upper Class
Class does have its privileges, and those who have power can break the rules. A woman with sufficient social class can be a warrior on the grounds of defending her husband’s or father’s interests. Just as some noblewomen ran the estates of men who were dead, away, or unable, a tiny handful of noblewomen control the military affairs of absent, dead, or infirm husbands or fathers. These women are generals, not warriors themselves, but an even tinier handful take it farther. They put on armor and lead from the front! These women can only get away with it for three reasons. They are rich and from the upper echelons of society; they are acting in the name of a man; and, once they begin, they are so competent that they gain the respect of other soldiers.
In even rarer cases, class has its privileges even when the men are still present. Some extremely rare noblewomen can accompany husbands or fathers into battle instead of acting as their surrogate. This, obviously, requires an exceptional husband or father to allow it. Sichelgaita, wife of Norman commander Robert Guiscard, will frequently take up arms and weapons with her husband (in less than 100 years). She will gain the opportunity by virtue of her tolerant husband and social position, but will keep it by her ability.
All this is a bit easier for pagans, since women have it a bit easier in paganism. Leif Ericksson's sister was a viking commander and warrior in her own right (her most famous exploit was charging into battle hugely pregnant and bare-breasted). The fame of her father (Erick the Red) and her brother’s and husband’s tolerant attitudes helped her gain the opportunity, and her ability ensured that she was taken seriously.