] The youthful infatuation of nineteen

I know I am a bit late on this one, but I have been thinking about your comment in relation to the word "of". I suspect Elinor considered that Edward had been much thrown together with Lucy during his adolescent years. Since he was how old? His infatuation of nineteen was the culmination of this, and probably the fear of being torn from his accustomed life and thrown back into the family shark pool.