I believe the ending is meant to be similar to Inception. Based on how Sun and Spears dont react with positive emotion I'm not quite sure Rose is seeing what we think shes seeing.
I am 75% certain shes hallucinating again.
I'm reading a lot about the lack of character development...it is not a book people...the development was in the actions.
Besides them not looking for weapons earlier I would say most of the action and responses to action were genuine, in the moment responses.