Scarlett Glenn doesn't want Fristy Davis to die now; she wants her to live, to live a good life.
Sometimes death isn't the most painful thing; living a life worse than death is far more terrifying.
Scarlett Glenn is very clear in her heart that what she's doing is very cruel, but what isn't cruel in this world?
Her mother was only 5 years old when Fristy Davis first 'killed' her; Fristy erased Aya's existence, and more than 20 years later, she erased Nell Harris's existence. What gives her the right to strip others of their chances to live time and again?
The pain her mother suffered that year, she wants to repay Fristy Davis twice over.
Even if Fristy Davis wants to die, this time she will not let her. She will not let her dirty her mother's eyes below.