So, it's a bit confusing. We know Mari switched their places essentially; switching appearances (but not names?) and brainwashing everyone into believing that the love they held was towards her and not MC (Alyssa at the time).
What's not clear to me is which appearance was switched to who, since in the spoilers it's been hinted at that originally MC was the one with golden eyes (hence why her eyes turn golden when she uses the spirits magic as Aisha). But in the flashback we just saw Alyssa is clearly still black haired and green eyed. Plus, It makes sense (from a plot standpoint) that the other siblings would initially dislike Mari as an outcast/illegitimate child.
If MC was originally the golden eyed child then it would make less sense if everyone suddenly loved her and for some reason Mari, the legitimate black haired green eyed child, was not. But then, why the similarities between Aisha and Marianne now?
Not to mention, when she was accused, Alyssa very clearly tried to reach out to her older brother, on account of them sharing both the same mother and father. By then, Mari had switched them, so what did the family see? We saw her (Alyssa) as dark haired and green eyed, did they see white hair and golden eyes?
In other words, when we're being shown anything involving Alyssa and Marianne, are we seeing the truth or the illusion created by Mari.
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What I'm trying to say is that the mirror scene explained NOTHING to me XD