I'm going to do this sort of poorly, I suspect, since Idothea is such a new character, but here are 8 Idothea facts:
1. She had a crush on Fang for a long time before convincing her dad (the king at the time) that it would be a good idea to give her to Fang in marriage. Basically, she thought Fang was hot and powerful. Then she met his personality...
2. She's led a sheltered life in which she hasn't had much tactical life experience, however, she's read a LOT of books (she rivals Derf in the category of ruling Linty book-nerd) and thus knows a lot of things from not-personal-experience.
3. Her culture is heavily suspicious/distrustful of magic, as well as elves, which became more acute after rumors of the "Great War" (Fang + Zedwig = everything asploded) came around. It isn't that unusual for open magic users to be executed for "witchery" or "devil horrors" or whatever, though not always. Her culture is also, in general, harsher than most. (See: Bob)
4a. She is incredibly imaginative and creative, but has barely scratched the surface of her potential.
4b. She is Scheherazade, and there's a story about how she gets that name, but I haven't gotten to it yet.
5. Zedwig inadvertently swept her off her feet with his intellect and natural interest in her learning. This also can be chalked up to her lack of experience (the ease at which she falls in love). Plus he's gorgeous, terrible at concealing his own romantic interest in her, and I guess Idothea has a thing for elves.
6. She trusts James. What could possibly go wrong?
7. She is far more manipulative/scheming than she allows herself to appear.
8. She likes both of them.
I'm not taggin' nobody! (rebels pointlessly)