A reader points out my unclarity. Women cannot participate in the sacrament of Holy Orders. This includes the diaconate, as well as the priesthood. My apologies. However, there is still no particular reason I can see from Ordinatio Sacerdotalis that a lay woman could not be a cardinal. It’s not permissible by canon law at present. But such law can be amended without doing any harm to the Tradition, so far as I can see.

Happily, it’s not up to me to decide. But I suspect its a question that will be raised sooner or later.