Charlie "dying" (or not) for a reason or for nothing is definitely something to keep in mind.
Kate told "Wayne" inside Sawyer's body back in season 2 when he was dying that she is attracted to Sawyer but knows it's wrong because he is a "bad" person, but as we've seen he has become better and less evil, especially now that he had his revenge against Cooper. Sawyer and Jack both really love Kate and that's why she can't choose, she doesn't know how to love back either unconditionally regardless of each one's circumstances.