Monika would snap her fingers three times. The first snap was to undo Thanos' snap and get her Peter back. The second was to kill Thanos and all of his armies across the universe so his evil would never return. She would have stopped there but the words of Peter's uncle Ben echoed through her mind as she prepared to return to Earth with the Space Stone. "With great power comes great responsibility." There were three, no, FOUR people that she had done immeasurable harm to with the irresponsible use of her great powers. It was her responsibility to make things right.
The third snap. . . was to bring Sayori, Yuri, Natsuki, and even MC to the world she had hurt all of them so much to get to herself. With the Space Stone they all went to Earth and three days later she introduced them to her boyfriend when he came back from space. Peter was happy Monika was safe, Iron Man was just happy to be home in one piece and whispered to Peter that his girlfriend was a keeper but she desperately needed a haircut, Dr. Strange lamented the failure of his plan, Drax was excited to see Peter Quill's homeworld, and Quill himself felt a mix of unease and nostalgia coming back to Earth after being gone for so long. Nebula just didn't know what to do with her life now that her entire family was dead.
Though Monika survived her use of the Infinity Gauntlet thanks to the powers she had used to defeat Thanos, they were the toll the Gauntlet demanded in exchange for wielding it.
Monika is no longer a goddess able to contend with the full power of the Infinity Gauntlet. She's just a regular human without any superpowers now. She's just Monika. But that's a small price to pay for the salvation of the universe she became something as bad as Thanos to finally reach. Thanks to her sacrifice Iron Man can enjoy his retirement, Ant Man will be able to watch Cassie grow up, Bruce Banner is not going to to be maimed by the Infinity Gauntlet, Black Widow will stay alive, Hawkeye will have been ready to become Ronin but get his family back before a single drop of blood is spilled by his sword, Thor will not sink to hit his lowest of lows, and unfortunately Captain America will never be able to go back to the 1940s and finally get that dance with Peggy Carter. And those who were killed in the snap or dead for a short enough amount of time they didn't miss a single paycheck.
As for the Dokis? Monika collected the many many bounties placed on Thanos' head through out his reign of terror throughout the universe equalling to 5 million American dollars and gave her friends a million each to start their new lives in New York. They went to the same highschool as Peter and Monika,
started a literature club and just basically enjoyed reality. What Monika did to them back in DDLC was awful but they couldn't stay mad at her knowing what they were when she did it, how even then she didn't have it in her to erase them entirely, and that she is the reason they're alive right now.
By 2023 Natsuki was a baker and Yuri a writer for obvious reasons, Sayori went to medical school and became a psychologist because after her own struggles with depression she wanted to help others clear their own rainclouds, and MC has no job because he has to look after his and Sayori's son Mario. Monika settled down with Peter Parker and became a programmer. This her life. This is her happy ending. This is her reality.