@mahpn I wouldn't say she hasn't achieved anything, she made friends, revamped her image with the noble ladies and the servants in her house, she secured a safe house from her maternal grandfather, and confirmed her lineage.
True, she hasn't really done anything that specifically targets Cosette, but her aim isn't 'revenge', it's to feel so comfortable in her own skin that she won't be pushed around like last time. As far as she knows, Cosette is her real older sister, not somebody she has to destroy.