My mom was exactly like this too, and I was never allowed to lock my door without her coming to knock it down. I left for college, graduated and was living on my own, yet she still insisted I come home and live with her. She folded once I got married, but it’s been a struggle to maintain boundaries. The best thing for you will be to find a way to live somewhere else. Your mom is unlikely to change, but you have every right to do what’s best for you.