The 24 hour engagement.

Her feelings and his intentions are two different things, IMO. I can understand her sense of betrayal, even though it was not his intention.

I also think that he really really needs to revisit his train of thought when he decided to tell her "no pressure" to get her to go on the trip, while planning the ultimate pressure possible... it was basically a deliberate lie designed to get her to be in a position she explicitly stated she did not want, and yet he seems convinced that it wasn't due to her saying she wanted to be surprised by what he had planned for the trip.

In that context, it seems obvious that the kind of "surprise" that would not conflict with the promise of no pressure would be something more along the lines of lobster dinner or a trip to the sea lion caves.