LOL IT MAKES SENSE IN BOTH CONTEXTS THOUGH
she said that she had a dream where she lost her and then became a reincarnation of the demon lord.
Mc thinks that Kay is saying she lost her(red-head version of her) and became the reincarnation of the demon lord(which she would probably be scared of after people have been trying to make her one)
Kay is saying she lost her(old friend version) and became the reincarnation of the demon lord(from a story. Though, Kay doesn’t know this is a story and only red head does)
So, both work in context and that’s why it didn’t signal anything to redhead mc. They both know what the demon lord is and how people have been calling Kay that, so it’ll make sense for her to say it and redhead mc to not think it’s weird
HOW DIDNT SHE REALIZE ITS HER FRIEND