Complex sentence: No one has received grace in such fulness, no one has co-operated with grace so faithfully as she, so the Church praises her as the Mirror of Justice (speculum justitioe).
Split into simpler sentences: No one has received grace in such fulness, no one has co-operated with grace so faithfully as she. It is for this reason that the Church praises her as the Mirror of Justice (speculum justitioe).