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.
In principle, it is not permissible for a widow in her waiting period to move from the house where she was living when her husband passed away without a valid and sound reason. However, if she is obliged to move, then there is no harm on her, as Allaah says (what means): {…while He has explained to you in detail what is forbidden to you, except under compulsion of necessity?} [Quran 6:119]
Allaah also says (what means): {…and has imposed no difficulties on you in religion} [Quran 22:78]
Moreover, the author of Az-Zaad, Imaam Ibn Al-Qayyim said regarding a woman in her waiting period who moves out of her deceased husband's house: "If she is afraid, or if she is forced to move, or because of a valid religious reason, then she can move to wherever she wishes." However, some scholars set a condition that she should move to the nearest house to her deceased husband's house.
Allaah Knows best.