Is a wife considered sinful for seeking divorce from her husband who has married another woman, was unable to provide her with independent housing, and forced her to live with her father-in-law who consumes alcohol, while she feels neglected by her husband and notices a change in his treatment of her?

If what the wife has stated about her situation is true, then she has the right to seek divorce, due to the lack of provision of private accommodation for her, and because she is being harmed by remaining in the husband's father's house. It should be noted that the husband's father is a mahram to his son's wife, and there is no harm in her living with him or being alone with him, unless she perceives something suspicious from him, in which case she should treat him as a non-mahram, or if she fears harm from him.