Does attempting to return to one's home country, despite parental objection and suffering from the new situation, constitute displeasing God, and how can one know the most suitable place for them?

The best country for a Muslim is one where they can be most obedient to Allah. Therefore, Muslims are prohibited from residing in non-Muslim lands. If the sister is married, she should live with her husband, unless her staying with him involves disobedience to Allah. If she is not married, she should live with her parents and strive to be dutiful to them, for her living with her family is better than living far from them. The issue requires more details from the questioner.