So in addition to rewinding time, she can also freeze time. She's a full-on time master, huh?
Also, I'm not totally sure if I'm interpreting this correctly, but is the fact that her aunt and uncle have "white" hair supposed to indicate that that's Nagisa's natural hair color and she's just been dying it black in this "prologue" timeline? Or do her aunt and uncle just have white hair because they're old? (Even though they don't look that old otherwise.)