Often, when faced with even the most noble of quests, the people that are by our sides are the closest thoughts in our mind. Even on a mission as important as saving the very world, a single person is only as strong as the people they let into their lives, and if those people were to slip away, we would surely feel their loss.
You would never slip out of her mind... If the tables were turned, I should think that she would be just as lost.