Men have always overlooked and discounted her, because they view her as too small and unhealthy to produce children.
Marriage in the Dark Ages- and for most of human history- was based on whether the couple could produce living children. If a couple could not, it would seriously damage the life of their society because new generations of people were desperately needed, or the population would die out.
Her sister Saehild, however, is seen as healthy and fertile because she is tall and buxom. Aelfwyn is destined for a life as a stepmother, a nurse or a maid, until she meets a certain red haired Dane…
I imagine Aelfwyn as Emma Watson, English actor.