Sentence 1: Ellie was crushed that everyone but her was invited to Katy's party. 
 Sentence 3: Ellie realized that she was supposed to be invited 
 Sentence 4:  She told Katy she hadn't gotten an invitation but she could go 
 Sentence 5:  She felt much happier that she had been left out by accident 
 Option 1: The day before the party Katy asked her why she hadn't RSVP'd. 
 Option 2: She decided she didn't want to go to Katy's party anyways.