Elmo bhai,
I must confess, i don't know who Nazia Hasan is. But from your post it sounds as though she was some kind of musician or singer.
Anyway, that's besides the point.
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ke guzrey hoey insaan ki rooh ko takleef pohunchti hai..
[/quote]
The only pain the soul will suffer, is that in the grave, for sinful acts he/she engaged in during the life of this world. Words uttered by people, following ones death, do not effect the soul of the deceased in any way.
However, with regard to your question and that whether it is permissible to speak ill of a person following his/her death, then this is a broad topic. If he/she was indeed a clear sinner, then it depends to what extent they displeased Allaah and whther becuase of the practices of that individual, he/she now has a following or support of some sort. In this case, becuase the act was haraam, then his/her fans need to be clearly warned.
However, this warning needs to be carried out by wisdom. Remember, it is the evil actions of the person to which the objections need to be related with, and not the person himself/herself.
Nevertheless each situation is unique, and we need to look at it in its own right. However, even after saying all this, there is a hadeeth of the Prophet (sallallaahu 'alayhi wa sallam) tat mentions not to speak ill of the deceased and what he/she did in this world is now between him/her and Allaah. I'm sorry i paraphrased, and don't have the reference for this with me.
.... and Allaah knows best.
regards
"No leaf falls except that He knows of it, and no rain drop forms except that He has willed it."