Some questions about The Premonition by Banana Yoshimoto

I’ve recently finished this book, found the prose very beautiful. I had a few questions about some of the events that I didn’t quite understand.

1. Why did Yukino leave after talking to Yayoi that she was her sister?

When they next met, I feel they didn’t talk about Yukino’s leaving much, and so I’m still trying to interpret the significance of it.

1. How would you describe how the Yayoi’s newfound memories changed her relationship with her aunt? This is something I’ve been trying to chart out.