>>2329793She's different, but only different as in you're different from yourself when you were aged 15, 8 or 4.
Rei dies, her body is gone. It's dead, just a lump of matter, atoms and molecules at the higher order of the chaos ladder. But look at that, even if her entire physical existence she can see, touch and feel is gone, she still remains!
Her body and all that is replaced. She lives again, but changed forever by the experience and the fact that her memories are lacking.
The beautiful thing though, is that even if she should have nothing physical or biological tying herself to her old self, she can still remember and feel that she's cried before. Her emotions and the very core essence of her being is still there.