Sentence 1: Joyce was at the mall. 
 Sentence 3: Joyce waved to her but received no response 
 Sentence 4:  At school the next day, Joyce asked Jill why she didn't wave back 
 Sentence 5:  But Jill just didn't see Joyce 
 Option 1: And she saw one of her classmates, Jill. 
 Option 2: She did not see anyone she knew at all.