For me, I think what she first saw in Scott was his ability to be his own person, and take life by his own accord. She muses in the opening chapters about how freeing it would be to gain her personal freedom but that its cost was far greater than deciding upon walking in shoes or being barefoot in a city that was bent against abandoning propriety. She in turn, was caught by his ability to appear standing outside the sphere just shy of what she was accustomed to finding,... the familiarity of what she was bred to understand and what she originally felt she would accept as her way of living. F. Scott Fitzgerald ignited her deepest desires to live a life outside the boundaries of schooling as a Southern-bred debutante,... making her yearn for a carefree life of living through her dreams rather than her obligations.
I think what she saw in Scott was at first what she dreamt would be his future, due to unearthing his own desire to succeed as a writer, and inside that moment, she saw herself gaining the confidence to dare to be something more than what she was originally expected to become... a child bearing housewife with a full social calendar. A life that I think after meeting him, felt empty and hollow, less alluring and lackluster in its appeal.
I personally think if the passage about her readings were true, the affirmation that one destined to be great must not be held back set the course for her future moreso than any reckoning or desire that she might have bourne herself without its knowledge. I think that affirmation gave her worth and jettisoned her on a course to help shape someone else's destiny, almost before she considered her own fate and what she could do with her own gifts.