Still bad idea for so casually spending time with your fiancé’s brother privately. At least have another person to witness nothing happened.
The hints of her becoming interested in Theodore also not typical with otome stories. In this, she doesn’t consider Jade “betrayed her first”, she still want to save her relationship with him.
Typically otome stories would make the mc consider the old relationship is done first, so they’re not “cheating” which would weaken their moral standing.