Yeah, that’s a difficult part, and I just imagined it as “I magicked the magic, and now you can’t move.” I think the one brother did split up, to corral the group into the center, and that’s when the crystal appeared to keep them from moving.
As for Usagi’s line, I think it helps a little to split the sentence on けど, and then un-invert the second half of the sentence by moving the は topic from the end to the front.
- このお姫さまか知んない
- けど
- あんたの親は知ってんの
I took 「このお姫さまか知んない」 as “I don’t know about this princess thing,” but I can’t really a reasoning why into words.
I parse 「知ってんの」 as 知っている + の (questioning) = “Do (they) know?” If I have it any bit right, then I think it makes more sense when connected to the rest. “Do your parents know!! The trouble you’ve caused us!”
In all, I took it as, “I don’t know about this princess thing, but do they know? Your parents! About all the trouble you’ve caused us!”
Or, a little more smoothly in English, “I don’t know about this princess business, but do your parents know about all the trouble you’ve caused us?!”
Looking at the 90’s Tokyo Pop translation (which is often not reliable, but looks pretty good here), they went with, “I don’t know what you’re a princess of, but do your parents know what you’re up to!! All the trouble you’re causing for us!”
The 10’s Kodansha translation went with, “I don’t know what you are a princess of, but do your parents know what you’ve done?! You went around causing problems for everybody!!”