CM brings up "flash point" or whatever they called them as checkpoints for transportation, which is what they were using to travel huge chunks of space so quickly, and what she needed to lead the Skrulls away from. However long she was off doing that for (presumably it wasn't the entire 20 something years but who knows), she was making a point to get considerable distance away from where she already knew hostiles would get to Skrulls.
When Sam Jackson was asked about the pager, he said something along the lines of "Who says he (Fury) didn't?", which could have been a smartass quip but some people are under the impression that he had used it during both Avengers movies, but called her off when each situation was under control (iirc both the NYC invasion and Sarkovia city drop began and ended within hours), and from the time it took her from whenever she was during the rest of the MCU til she arrives in Endgame (also, from the looks of it, apparently weeks or months after the events of Infinity War) and was never called off, she assumes serious shit has happened.