Keep in mind that there are many factions of the Rebel Alliance, so I don’t see why she has to be everywhere Luke, Leia, Han, etc. is.
I have to point out that this is not true in the original movies. I suppose this might be suggested in the EU stuff, but in the original 1977 film, the Empire is attempting to find one hidden Rebel base and Darth Vader is confident that destroying that one base will result in the end of the Rebellion.