i'm not gonna add anything else to my forum unless absolutely necessary. i've lost editing access in the past and don't want that to happen again, and it's also very messy. i have been interested in a copycat type plot for a while. i'm thinking for a bit, probably during kit'hood, she tries mimicking saccharine, her demeanor, her actions, down to her looks. she cannot comprehend her mother's favoritism at that time, she only becomes aware after, so she thinks that if she acts more like her sister, she'd receive the same praise and love that her sister receives, but alas, it would be fruitless. her sister always had the upper hand; her mother and her 'love' for her. with whimsy doting on her sister more, her sister is bound to get more attention, and serein's 'sweetness' is just sickening. she'd be an apprentice when she lets go of her facade and will go back to shyly lurking.
may add more in the comments.