This could have been superb, but films with fragmented nonlinear timelines require more care to tie the pieces together than we receive in Orphan. It's a drama depicting major traumas in one character's life, but in reverse time order, inside a wrapper that begins and ends in current times.
Portrayal of the progressively younger main character Renée/Sandra/Karine by Adèle Haenel, Adèle Exarchapoulos, and Solène Rigot were excellent as expected, and young Vega Cuzytek played the child version, Kiki, with skill far beyond her years. Technical aspects of the film were fine.
But completely lacking is anything that provides a causal link from Kiki's experience to her mindset and behavior as Karine. I interpreted Kiki's trauma as one of misadventure, and not one in which blame is due. Nothing in the film shows otherwise. And the drastic change in personality and behavior of her father is given unacceptably short shrift. The end of Karine's tale, her transition to Sandra, and the transition from Sandra to Renée also could have been depicted more explicitly, but the gist should suffice.
Other than that, once viewers understand that these women and girl are the same person, the film is accessible. And unlike some folks, I interpreted the final scene as redemptive, with Renée facing up to what is required of her while having hope and honest intent to return to her newest responsibility when she can.
It's worth watching!