What is the ruling on the behavior of a wife who is bothered by her husband's sick parents visiting their home for treatment, and what is your advice for preserving the marital life?

What this wife is doing is not befitting people of good morals. It would have been better for her to encourage her husband to be dutiful to his parents and to be an aid to him in righteousness. Her service to her husband's parents carries immense reward, for it is service to a Muslim, and through it, she gains her husband's pleasure and acts kindly towards him, and in that is obedience to Allah Almighty.