Possible Clues:

• 'My ___' (#1 hit for the Knack)
• The Knack's girl
• Title girl in a No. 1 song by the Knack
• “My ___” (1979 #1 hit for the Knack)
• "My" girl in a 1979 hit
• Title girl in a 1979 #1 song by the Knack
• 'My ___' (1979 hit by the Knack)
• The Knack "My ___"
• 'My' girl in a 1979 hit
• ''My __'' (#1 song of '79)