
Kokuto:
Let's be honest. FFB is so much more fun than XL. And none of her family is trying to kill FFB... though they should be, if they weren't clueless. And the best part, is he really IS XL.
FFB is the escape route for her scenario of being with XL for long term.
My impression from the novel is that she loved XL(more than FFB, but anyway later she knew they are one person, FFB was XL without military duty, XL was FFB at the frontline). She first paid attention to FFB just because FFB looked like XL. She spent ~ 2 years hanging with FFB in Xuan Yuan capital. It was just friendship. During that time, she was more dominant in that relationship.
But when FFB got into her room and revealed his true identity, she felt relieved. By the way, when he sucked blood from her wrist, XY felt pleasure. The previous time that TH used this word is when XL sucked her neck in the pool (via the feeling of CX). After that, when she met him again in Middle Plain, they continued hanging out, learning archery. She paid more attention on his temper/attitude. Then he was the dominant one in the relationship. Also, in the novel, TH always descripted XL's appearance (she used many words to descript his handsomeness) whenever he emerged. That was actually XY's observation. But TH did not descript FFB's appearance at all (only clothes).
Additionally, she had affection with XL since the time in QS town, isn't it? I had the feeling that first she had crush by his appearance. She had kind of instinct attraction to XL