Is it permissible for a woman whose husband is in a coma to go out with a mahram, such as her nephew, to public places?

A woman must know that her home is her abode, and she should not leave it except out of necessity. It is permissible for her to go to the market, the hospital, or the Haram. The fact that her husband is in a coma does not affect this, unless he, when conscious, only permits her to leave out of necessity. The rulings of the 'iddah (waiting period) are not binding upon her, because they are contingent upon actual death, not a coma.