Just so we're clear, they would be step-sisters, her father would have had a whirlwind romance with her mom after Rosie's mom died, so LOTS of hate (at first). I assumed they would be the same age, but older works as well! And as far as pbs, it really depends on personality--but I pictured her a little more tomboyish, or anything to contrast to Rosalind's dark, princess-y, disaster bitchiness.