That's sort of a misnomer, as of course women were more than capable of creating art, but were they allowed to be artists, or were they restricted from fields like painting, sculpture, music, etc. in the Middle Ages? I mean, did nuns engage in book illumination like monks did, or were there prejudice against women being artists in Europe during the medieval period?
So, not being a medievalist, I can't do justice to this question myself. However, as a musician, I do know of Hildegard von Bingen, a medieval female artist of great renown. And so, I'll link you to a post by /u/sunagainstgold about some of her exploits, and perhaps they will be able to fill in the picture more about female artistry in medieval Europe!