What is the main conflict in Perfect Mistake by Kate Brian?

Ariana Osgood, an escapee from a women's prison, is happily enrolled at an elite school. She poses as Briana Covington, a girl that Ariana killed in order to assume her identity. Her life seems finally on track as she has a set of entirely new friends and a wealthy grandmother footing the bills. Ariana has gone to great lengths to secure this new life, including stealing from other students in order to pay off Kaitlynn Nottingham who also escaped with her. However, Kaitlynn shows up as a student at the school due to a large donation made with the money Ariana stole. Kaitlynn poses as Lillian Oswald and Ariana is not happy to see her. The girls wind up as roommates and Lillian begins making demands on Ariana.