Sentence 1: Kate was spending time with her boyfriend. 
 Sentence 3: Suddenly, she revealed that she had written him a song 
 Sentence 4:  She performed it for him as he listened happily 
 Sentence 5:  He thanked her for the song and they felt even closer 
 Option 1: He was showing her some of his favorite songs on the guitar. 
 Option 2: She was showing him some of her favorite songs on the guitar.