The Speedrun Manual of Miss Witch

This never happened. Stop inventing things.

In chapter 42 she check the menu for the first time, the predicted date is June 20, 7:00PM.

In chapter 43, after she paid for and launched the simulation, she starts the simulation at June 20, 6:25PM because the simulated self just died.

There was never a moment when the date in the menu changed.

Her action in reality caused the perpetrator to advance his plan. What she would be doing in the simulation had absolutely no bearing whatsoever on what date the system would offer.

Beside you're under the misconception that the simulation endpoint offered by the system will be close to when she would die. It's not the case. It can't simulate past her death for obvious reason, but before that it can be anything. This is clear in the first arc, where after getting the Avenger archive she was in no actual imminent danger of death, but her next simulation was only one day in the future.

But at that point she had the power to avoid that death. There might have been unforeseen consequences if she just went blind, but probably none that would see her die immediately.