question for week 1

While reading the first ten chapters of MiddleMarch, the difference in the characteristics between Dorothea and Celia made me ponder. The two are in similar ages and have experienced similar life experiences, however, while Celia was more an ordinary girl, Dorothea strongly embraces abstinences, which eventually led to her to the rather too idealized marriage with Mr. Casaubon. But I wonder: what is it that shaped her belief as such? What might be some other elements that shaped Dorothea's believes?