Judith Jesch's Women in the Viking Age has a chapter on this topic, and is a good book overall for women in the (you guessed it) Viking Age.

She notes that in Saxo Grammaticus (the major12th century Danish historian) and in many of the Sagas and Eddas there are numerous women who act as warriors. The caveat being that these are all from semi-mythological, pre-historical, and/or literary stories and so it is difficult to pin down the truth behind them. As she says

none of these texts can be used directly as evidence for the history and culture of the Viking Age, they first have to be put through a sifting process in which they are studied as the literary products of twelfth- and thirteenth-century Iceland.

The idea that women engaged in violence, especially within the context of family feuds is not too far-fetched, but it would not have been normal. After all, the times when women warriors appear in sagas and stories are extraordinary not normal, these are women who defy the norm.

When we actually look for contemporary historical evidence we are in a bind, as the Vikings were pre-literate, all of our sources are Christians (and Muslims) looking inward. They don't say much about women at all, and certainly not in the case of the Vikings (who are typically called Northmen or Danes). There is, however, an interesting reference in Regino of Prüm's Chronicon for the year 873, (here translated by Simon MacLean )

the Northmen became excited by the pillaging of a few cities and territories and realised from the plunder available in each how much wealth they could get from all of them. They entered the city of Angers and found it empty because its inhabitants had scattered in flight. When they saw that it was impregnable because of its very strong fortifications and due to where it was sited, they were filled with joy and decided that it would provide a secure refuge for their people and their troops against those people who might be provoked to war. Immediately they brought their ships and the River Mayenne and moored at the walls, went inside with their wives and children as if they were going to live there, repaired the damage and rebuilt the ditches and palisades.

So there is textual evidence (here and elsewhere) that Scandinavian women accompanied their men on raids to the Continent and also to the British Isles. Whether they were fighting or just preparing to settle is another matter.

Odds are the second is much much more likely, given both the paucity of any mentions of women warriors in contemporary documents and traditional gender roles in the Middle Ages in general. Seaver is almost certainly correct in her assessment. Everyone in the Middle Ages had the capacity for violence (heck everyone does now...) but active participation in raiding and warfare was largely (in not entirely) confined to men.

Hope that helps!