A woman lives separately from her husband. Husband never took care of her or children and did not see them for 3 years. Now he died. Does the wife needs to sit in iddat? She is not divorced.

Yes, she need to sit in iddat for 4 months and 10 days. Sitting in iddat means she do not get married during this period, and she not to wear fancy dresses…etc. But if she needs to work to feed her self and her pendants, then she can do so.