All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
The scholars differed in opinion regarding the ruling on the husband preventing his wife from visiting her parents. The view that we adopt here in Islamweb is that the husband should give permission to his wife to visit her family unless he is afraid that they might corrupt her.
The length of the visit and how often it should be is a matter that depends on the customs and traditions, and it differs according to the circumstances.
Therefore, if you allow your wife to visit her parents every year and to stay with them for one month, then you are kind to her, and you are not obliged to give her permission to extend the visit to two months.
Our advice to your wife is to fear Allah and to thank you for your kindness and not ask to you to do what you are not obliged to do.
Allah knows best.