My concern would be simply that they will not have the authority to make the decision locally in Spain, and need to speak with 'control' in the UK, who would roll out the party line and say their 'policy' is no visa no travel. Whether one is needed or not they can still have an outdated rule about who they choose to accommodate on their planes and come up with an excuse for it being there. Yes you may go to court that your wife was refused travel but their corporate legal team will probably decide it is worth sitting out.
I think I would jump in a car and drive to Calais and deal with UK Border directly.