Whenever you see a woman in all black, don't assume she's a widow. She may be wearing a fashionable black dress, especially if it's shiny black and fashionably trimmed. Even if she is clearly wearing mourning black, she could be in mourning for a relative or other very close person. Wearing a black and white crape cap apparently is reserved for widowhood, and not for other forms of mourning. The length of time for mourning others is also shorter than for a husband.
Men have it easy when it comes to mourning.
Wearing a black arm band for 3 days is all that is expected for the death of a man's wife. If he has young children he is encouraged to remarry as soon as possible so the children have a mother to raise them. On the other hand, a woman shouldn't consider remarraige for at least a bit over a year. I hope this helps you with your impression. Feel free to ask specific questions as well.