I have a more simple theory. There is a empty room because at the last minute a girl who was supposed to come has cancelled. About Nicole she is back because she asked RLC to bring her back to her spanish lover.
I think and i hope RLC is now more requiring when they cast girls. They don't want shy girls
Nicole and Rose met in the corridor just as Rose was about to leave the apartment. They said "hello" timidly without even looking at each other. Miss X also there. I don't think she said "hello " to Nicole
if think they will be back next 3 hours. They went to the beach very close of their location.
Off course that does not mean that after the beach, they will not take a shower , change clothes and disappear for the overnight