What is the meaning of 贅沢 in this sentence? Context: the writer is talking about going to a cinema that has just opened near her house. > … **** Why is going to the cinema early in the morning after staying up all night a luxury? Does have a different nuance here? Thank you for your help!

This means a luxury experience, and it seems to refer to watching the movie in the large theater alone as if she had rent the whole room.

As you suspect, the order of the sentences is a bit unnatural, and could have come right after the first sentence.