Is the wife held accountable for refusing to go to her husband's hometown in Upper Egypt due to the difficult living conditions there, such as lack of cleanliness, insects, scarcity of water, and poor sewage systems, which cause her and her children illness and hardship?

If the wife's staying overnight at her in-laws' house causes her harm, then she is not obligated to obey her husband in that, nor does she sin by refusing. This is because obedience is in what is good and not in what is harmful. There should be mutual understanding between the spouses, as the foundation of the relationship is affection, compassion, and consideration of circumstances. Part of good companionship is the wife's kindness to her in-laws and her assisting him in honoring his parents.