Shallan Davar and Arya Stark.

I chose these two because their family backstory is similar yet the complete opposite. Arya would have hated studying with Jasnah, but Jasnah would have realised that her talents lie elsewhere and that she could be helpful to Dalinar, and so they would go there anyway. Arya would have been very unhappy initially, amd would resist any real duties and instead mope about missing her family, but eventually I think she would find a good father digure in Dalinar, amd realise that family is what you make it. She would help destroy the Ghostbloods in revenge, and she would be the one to kill Sadeas. After meeting Kaladin and hearing about his brother and Amaram, she probably would treat him like her own brother, amd in realising what the world is truly like and finally grow up as a person. Unfortunately however, her hatred for the people her wronged her family would consume her and she would become a servaant of Odium in order to embrace it.

Shallan would probably never have run away from Kings Landing like Arya did amd would be forced to grow up very quickly. However this would be beneficial as she would meet Tyrion. Their love of history would encourage each of them to actually examine the Others myths amd the dragons and magic of the world, rather than playing the game. However, Tywin being Tywin he would ignore both of them when they reveal the truth about the Others. Instead Shallan will go to the Wall where Tyrion is alresfy in contact with Jon and they would actually do something to stop it, like she did with UrithuruI. Having both dealt with abusive fathers, I think Shallan and Tyrion would fimd each other as kindred spirits amd finally learn to deal with those issues.