Both are possible. The necklance is obviously the only thing connecting all the mishappenings, so it has to be the key, also the last finance when she was begging the prince, she had a purple glow in ber eyes, just like her father, when he attacked the fl. So maybe they were controlled through the necklance, and since she had an item from a which, and was controlled by one the tree reacted as if she was one, even tought she was not. And maybe she did not even realize she was controlled, and thats why she did not understand why the tree reacted. She may had her conciousness, but was controlled and manipulated in making her decisions through the necklance is my theory. (=・ω・=)
Spoilers say the Queen is actually like a queen bee. She plants "seeds" to turn girls into witches. These girls then become infertile and lose appetite also. Apparently, the Empress inherits a holy sword after becoming Queen. This sword can kill her but witches can't use it so I guess that's why she keeps turning his fiancees into her pawns
Lipilu. Oh my god. Thats crazy. But next time pls be a bit more careful with spoilers. Like make it so that the word spoiler and the spoiling content are a bit further from eachother, so those who want to avoid being spoiled can stop reading. ٩(๑❛ᴗ❛๑)۶ but I was glad I read your spoiler, it answered some of my questions.
No worries. Also I like thinking of possible theories about whats gonna happen,so it was my intuition.
(=・ω・=) Also it's just an advice for future comments, since there are quite a few people, who get really angry over being spoiled. I like being spoilt, but some will spit out curses, even if they had read the warning. Once I posted similar to you, a comment of spoilers I read in comments from others, but made it so that they were warned and had to scroll down in the comment to read the spoiler, but some still cursed at me for spoiling them, even tought I clearly wrote spoiler before the content. But thankfully some others protected me saying its their fault for reading despite clear warnings, not mine.(⌒▽⌒)

i feel so bad for the prince's previous fiancees, they were (probably) killed because they were thought to be witches - even though it was (probably) those stupid necklaces that they were gifted (⊙…⊙ )