What legal action can be taken against controlling, abusive parents?

My girlfriend and I were in a live-in relationship for over 3 years, but her parents separated us. They are threatening and controlling her life—taking her phone, tracking calls, messages, and GPS location whenever she goes out. Her brother and another person have access to her personal accounts like Google, Facebook, Instagram, and bank accounts. They forced her to lose her job, prevent her from going outside alone, and subjected her to emotional torture, making her mentally disturbed. She feels suicidal due to this situation. She is ready to marry me, and so am I. Please suggest any legal action we can take.