Do you really only know how to appreciate something after losing it?
She loved him without regrets, but she never got his love until her death.
He fell in love with a girl who didn't love him, and therefore ignored her love for him. It wasn't until she used her own life to save the girl she thought she liked that she realized that she had fallen in love with her unknowingly.
However, everything can only become a memory. Maybe, for her, memory is enough.