Is she sinful for confessing under duress to actions she did not commit, which led to her divorce?

Lying is forbidden and is a major sin, and the one who commits it without necessity is sinful. If a wife fears for her children from her husband's harm or killing, and she has no recourse but to lie to him, then there is no sin upon her. Al-Nawawi said: "Speech is a means to achieve objectives. Any praiseworthy objective that can be achieved without lying, then lying for it is forbidden. But if it cannot be achieved except through lying, then lying is permissible." A husband accusing his wife of something she is innocent of is a great evil, especially accusing her of adultery without proof, as Allah Almighty says: "And those who accuse chaste women and then do not produce four witnesses - lash them with eighty lashes and do not accept their testimony ever after. And those are the defiantly disobedient." And slandering chaste women is one of the seven destructive sins.