What is a significant choice that Irene makes

Irene makes a few significant choices. She decides to allow Clare into her social circle. She stands aside and allows her husband to carry on an affair with Clare, and in the end...... she chooses to murder Clare rather than expose her. In her mind, exposure would give Clare's husband grounds for divorce...... freeing her up to not simply have an affair with her husband, but to possibly be set aside by her own husband..... in favor of Clare.