((Unless I'm misunderstanding things, and I certainly could be, I'm still in Friesden's mind. Well, mentally anyway. Carrot is likely to be absolutely ignored by Khenal right now.))
"Please, Friesden, I just want to help you. If your father wants to hurt you, he'll have to go through me first."
********
As far as Friesden's true character, it seems a longshot for her to be manipulating everyone at this point. The schism of personalities in her Diary would take a schemer of the highest caliber to even put to paper. After all, it's her diary, for her eyes only. The words of meek Friesden appearing in her Diary suggests magic, and Friesden is no alicorn or unicorn. She theoretically could have a magical accomplice, but that seems a bit out of left field. You could still pull off the schemer, but this level of schemer is very difficult to write, especially with multiple people writing their stories as well.
I will say this, though: You are at the crossroads for your character. If she's a schemer, this could be her opportunity to avoid punishment for her crime by blaming it on her "darker half." Khenal is too much of an idealist to allow "meek Friesden" to take the punishment that her dark side deserves. She'll be free to continue her experiments, but will need to be extra careful; it's unlikely she could fake her way out a second time. If she really does have a schism of personalities, and the dark side wins, she'll get to face the full punishment of the law. If her good side wins this encounter, she'll likely get off punishment, but have to deal with the shadow of her darker side waiting for her to slip again.
Or you could think of something totally different and completely awesome. Like I keep saying, she's your character. I can give ideas and try to inspire, but you decide how she really will be.