She went to Earth first. That was in one of the Captain Marvel credit scenes.
Bruce Banner knew that Tony Stark, Peter Parker and Dr. Strange were abducted. Rocket knew that the other Guardians were going to Titan. So it's not really a stretch to ask her to look for survivors there.
I think the film suffers from the same issue that The Dark Knight Rises does, in that they've been a bit ambitious and ended up with a film that was far too long. They've had to cut things that would help make some things a lot clearer. For example, in the The Dark Knight Rises...
That said, I love both films.