What is the ruling on a woman who did not complete her 'iddah after her husband's death, having left two days of the 'iddah, and what is the ruling on one who did so intentionally versus unintentionally?

Whoever misses two days or more of her waiting period (iddah) due to forgetfulness or ignorance, there is no sin upon her, and she does not have to make up what she missed, because the waiting period cannot be made up. However, if she did so intentionally, she is sinful and must repent to Allah Almighty.