When you first meet her, it’s early on in the game. She appears to be on the side of good.
She allies herself with Miriam against Gebel.
And helps her with certain items and whatnot near the entrance of the castle.
But you soon start to notice that there’s something weird about her.
And she turns out to be the true mastermind on the evil in the castle. Alfred is among the first to know this and challenge her openly.
But she bests Alfred and her boss battle is pretty tough. It took me two tries to to defeat her.
After her defeat, she summons some kind of big demon thing to be the final boss. Once you defeat them both, she perishes for good.