Please do not ask multiple questions. This is completely against enotes policy. I have edited your question to focus on one of your many questions.
The answer to the question above can be found in Chapter Fifteen of this excellent novel. We are told that Edna enters the dining-room late one evening, as was her custom, to be surprised by the "animated conversation" going on. As she sits down, she is told by several people almost straight away that Robert was going to Mexico:
As she seated herself and was about to begin to eat her soup which had been served when she entered the room, several persons informed her simultaneously that Robert was going to Mexico.
Edna is "bewildered" to hear this, because Robert had spent significant time with her during the day, reading to her in the morning and spending time with her at the beach in the afternoon, and had never informed her of his plans to travel. Note what this suggests about the character of Edna. She is so self-absorbed that she finds it hard to accept that Robert might have plans that do not include her.