If a woman neglects the mourning period for her husband, is her waiting period valid?

Question:
Honorable Shaykh, a questioner says: A woman in her forties lost her husband and did not do any of what Allah commanded regarding mourning for her husband, and after a period of time, she married another man.

Answer:
If she has completed four months and ten days, which is the waiting period for death, she may marry. Mourning is obligatory during the waiting period. If she neglected it because she was forgetful or ignorant, she is not sinful. If she did it intentionally, she is sinful, but the waiting period is valid. Yes.