Justice for The Side Character

Celestina Ashdown is a side character in the novel "The Prince Lives For Me". She's the character that Liliana love the despite being a side character. But why is she suddenly inside Celestina's body?

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"Nobody can touch my daughter. Cut off his wrist."


"What are you talking about? Celestina is a peasant? I'll make you a peasant."


"How dare you bully my sister."


And why are all the villains so eager to see her?