19yo HS student forced to marry a 19yo crowned prince. She was isolated from her family, from society and forced to live within prison-like rules within the palace. She developed affinity towards a narcissistic crowned prince who does not accept faults and finds a way to blame everything to the FL. I find it inconsistent for the FL to fall for a mean guy. She lived in a harmonious family and she has many friends. Unlikely that this kind of personality would want to have the high drama a narcissist brings.
All throughout the show, she wants to feel accepted by the ML. She gears towards an abusive relationship with ML's detached and self-centered personality.
I know she's making a great mistake and totally understandable because she's a child. If there will be a season 2 where they are middle aged person, I know for sure FL and ML would have already separated and high hopes that the FL finally learned what's good for her.