Is the wife considered sinful if she refuses to stay overnight at her in-laws' house due to its uncleanliness and the presence of insects and cats, in order to protect her child, and does this prevent her from honoring her husband's family?

Responding to the husband's request to stay overnight at his parents' house is not a religious obligation, but it is preferable to do so if it does not entail harm, as it strengthens the marital relationship and avoids problems. If refraining from staying overnight does not prevent the husband from honoring his parents in other ways, then there is no blame in that.