The first encounter, where Lucy tells her secret as they walk to the cottage from Barton Park, seems casual because we were not in on Lucy's thought process as she contrived it all. She had to get Elinor alone, where no one could hear them, where they would have uninterrupted time, and then she needed to have her 'props' with her--Edward's picture and his letter (maybe she always carries them, maybe not).

The next time, we are in on the planning process as Elinor tries to set up another meeting at a place where secrecy, and intimate one-on-one conversation are next to impossible.