How do I (28f) find the courage to tell my twin (28f) that I want to live alone?

My twin sister and I have lived together for nearly most of our 28 years of life, excluding a semester or two in college.

We’ve always had roommates, but I’ve gotten to the point in my life where I would like to finally live entirely on my own; I’m an introvert and function best when I am alone.

However, my sister wants to start focusing on finding a new apartment for just the two of us and I really don’t want to do that anymore. As a kid, I always thought living with your twin for the rest of your life would be the best ever. As I age, I can see how that is REALLY not good for us — but I don’t know if my twin sister can see that.

I would describe my twin as sweet and compassionate, yet co-dependent and emotionally unstable. She struggles to self-regulate, hasn’t ever been in a romantic relationship, still sometimes speaks in a childlike / baby way, and has a hard time being completely alone. Our adult relationship often reminds me of our childhood relationship, particularly how she sees me as her security blanket. AND she acts weird whenever I start getting serious with someone — sometimes she will make absolutely zero effort to get to know my partners.

I love her and care about her deeply, but I want out! I want to experience living alone so badly, and I think it would be better for the both of us.

But I’m scared of her reaction. I feel immense guilt. I know this all sounds obvious — just set the boundary and live alone!!! — but my heart feels like it’s exploding with guilt and grief.

tl;dr: how do I tell my twin sister I NEED to live alone?