Hello NeverHappy. I am sorry that you're having such a tough time I think it could be really beneficial for you to read about boundaries. There are a lot of great articles out there on the topic. Here's just one of many
How to Respect Other People's Boundaries

There's also another concept you may like to read about. It's called 'negative empathy.' Here's a link to a good article that I found useful in my life: Negative Empathy | Psychology Today

Your love for your sister is wonderful!! And when we love someone, we need to honor and respect their boundaries. Her choices to go out/not go out, kiss a guy/not kiss him etc are her choices. You cannot make those choices for her even if you believe they are not the best choices for her happiness. Only she can determine that. She's on her own unique path in life just as you are on yours. Boundaries are not specific to certain countries or cultures. They are important for all of us. They help us to feel respected and safe.

Please take a step back from informing your parents of her actions. Those are her private choices. If she wants your parents to know, she will tell them herself.

With regard to your coping, have you ever tried guided meditation? It really helps me when i feel anxious or confused.

She is lucky to have such a loving brother. Feel free to let me know if you find any articles which resonate with you regarding boundaries. I wish you and your sister peace and two bright futures