We aren't told exactly how, but at the end of the credits, the sky turns from red to blue.
I guess it's up to interpretation but after she was returned she was probably able to interact more with the world arranging people's outcomes, and it eventually led to the world never being destroyed. It's an open ending I guess.

世界是不完美的，但是人们心中的世界一定是完美的，所以美好世界前面才会有一个will前缀，指的是心中的完美世界，纵观整个游戏过程，每一封信件都在说着自己的倒霉事，同时也暗含了自己对美好世界的向往（will）否则我们也不会执着于s结局，但其实，s结局也不是美好结局，美好世界只在人们的will里，现实世界是不美好的，人们才会用意志will改变现实世界，让现实世界变成理想的美好世界，所以每一个决定都是有意义的，每一个决定都是在向美好世界前进，即便走的路是一条不完美的路是一条有遗憾的路。