Well, Fermina's father had arranged the marriage between her and Urbino to get her away from Florentino. During that period, young girls had to repect their fathers and all the males that had the upper hand so she really had no choice but to listen to him.

What really surprised me is that Fermina was the one who barely let out her emotions. She was very contained and that's shocking since psychologically speaking women are the ones who are more in touch with their feelings and they're the one who like to "connect more".

There was a sisterhood between her and her older cousin possibly because her mother died when she was very young and also her aunt who she would read to in the park when she was little also passed away, so she sought comfort and looked up to her older cousin.