I'm a little bit confused by your question. This is largely how women dressed for most of the period you're asking about. Early-high medieval clothing, for both men and women, largely consisted of loose, unstructured garments of wool or linen, worn in layers as dictated by weather. The length of the tunic/kyrtle varied over time, from knee to ankle length or longer, and details such as embroidery varied with wealth, but the basic construction of the article remained very similar. I can't see how it would present any more of a challenge to women's menstruation than modern clothing. Perhaps you're thinking of the clothing of a later era?