The type of sentence for the sentence “When night fell, she
went out to look at the stars.” is complex.
To add, a complex sentence contains an independent
clause and at least one dependent clause. An independent clause can stand alone
as a sentence and makes a complete thought and a dependent clause
cannot stand alone, even though it has a subject and a verb.
The allegorical meaning is most likely that the main character or person is trapped in a big problem in real life. A problem they don't know how to get themselves out of.