Try to find the real motive for her stay. Talk to your wife first. Discuss the matter calmly. You can talk to your in-laws too. Tell your wife that she needs to go. If she claims that you have made physical relations with her then ask her for proof. You need to handle this carefully because two families are involved in it. If she is staying over a year now then you need to confront her. You have to stand up for your marriage. You can’t just ignore her because it’s affecting your mental health too. And also no one wants constant conflicts in their house.