Anya was so kind to help me with a couple of additional links to suport the idea that women were indeed wearing Hosen.
This is a biblical scene and the lady in the middle is wearing green hosen. They seem to have some form of pattern.
There is another picture out of the Trés Riches Heurs du Duc de Berry. February you can see it here: http://historymedren.about.com/od/booksofhours/ig/Tr-s-Riches-Heures/February---Tr-s-Riches-Heures.htm
It is quite possible that also the lady in the front is revealing her hosen, but the coloring is so close to skin tone that I did not consider it a definite. Anya drew my attention to the lady in the back of teh shed. There you can clearly see the hem of the hosen, the color of which is indeed the same as the legs of the lady in the front.
Appenrently there is also written evidence as Henry the VIII aparently ordered silken hosen for his sister. But that is a second hand statement. I have not been able to verify this, so far.