This is an interesting question. From Foot’s own neo-Aristotelian ethical naturalist perspective, I don’t think she would accept executing an innocent person.

Her account of the practical rationality of the Sudetenland farm boy who chose death over joining the Nazis seems to indicate her preference for avoiding participation in others’ evil acts.

Just as well, it seems to conflict with virtues such as courage (giving into fear of a riot), wisdom (abandoning the rule of law to placate a mob), justice (murdering an innocent person), and so on.