Must a mother afflicted with Alzheimer's observe the waiting period (iddah) with mourning in the event of her husband's death?

If the mother is afflicted with dementia and has lost her mind, she remains legally a wife. She is obligated to observe the waiting period ('iddah) and mourning (حداد) if her husband dies. Her guardians must ensure she fulfills this, even though scholars differ on the obligation of mourning for an insane woman.