From what I know, her and her brother's magic are interlocked in a way which allows her brother, whom I believe, has little-to-no innate magic power, to use her abundant amount. However, I think she doesn't have a proper magic circuit which allows her to utilise her magic, thus making her extremely ill. And since they're interlinked as twins in some sort of magic, the brother is able to harness this magic, using her as a power source. And as the story progresses, its revealed that the brother found some sort of spell or something that severs this connection and instead gives his magic circuit to his sister so that she can fully function without him, however, killing himself in the process, thus why her condition was improving while she was away from him, this spell was in progress.
Also, the ML is a dragon descendant so he's not human and is naturally eqquipped with the ability to handle magic.
Thats everything from my understanding, anyone feel free to correct me if im wrong lol
You're basically spot on. Easiest way to describe it is that the twins are like one person split in two, when it comes to their magic. And its almost like said magic is trying to merge once more, which means one of them is destined to die.
im super lost about the whole twin magic?? at first i thought she was ill bc her brother took her magic all the time then he stopped doing that and she got better. BUT she was still always sick? and when she got away to lesset she got EVEN better. So ML is taking away some of her magic but she seems to be doing better?? oh and how does ml take the magic? like is he also magical but he seems to only be like sword magic good?? idk man im so confused.