If the husband of a woman has died, is it Haraam/prohibited for the woman to talk/see Maharim? If so, for how long?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

There is no difference between a woman in her waiting period (i.e. after the death of her husband), and other women in dealing with men. It is permissible for her to look and discuss with her male non-marriageable relatives but it is not permissible to look and discuss with others except for a need and within the Islaamic requirements and morals. Finally, we draw your attention that a non-marriageable person for a woman is the one who is eternally non-marriageable, among whom are the father of the husband and his son (from another marriage).  

Allaah knows best.