Multiple personality disorder question?

I have this adopted cousin and she is 5 years old now. My family adopted her from the boondocks where she was abused and badly treated by her mom (with post partum) when she was still a baby until she was 3. Her mom dropped her from the 2nd floor f their 2 story house and hit her with hard sticks. and now my pregnant aunt treats her badly too. My mom does everything she can but whenever we are out of the house, my aunt hits her. I admit i hate her too because I get jealous sometimes when she gets things but when I watched Sybil, I became scared and wary. Do you think she will acquire Multiple personality disorder when she grows up if my aunt wont stop in maltreating her? If well stop do you think the maltreatment of her real mom would still affect her?