How To Forgive Your Parents For Something Bad They done..?

Hi, I have a friend named Kc and almost a year ago her and her parents where driving somewhere then all the sudden their car blew up about a half a block from this woman bobby's house. Kc was able to make it out alive but can't say the same for her parents.. Kc then went to bobby's house to get help and whatever.. So now Kc was an orphan and she had no other family members like aunts or uncles or grandparents and no where to go.. Bobby then took it upon her heart to adopt Kc she was 14 at the time 6 months later Kc found out that an enemy/rival of bobby had put a car bomb under her parents car which killed her parents now the enemy had no idea that anyone was going to be able to live and for sure had no idea that bobby was going to be the keeper of the survivor that was not in the enemy's plan and bobby had no idea that there was even a bomb or had anything to do with her.. So six months later the enemy confesses to bobby what the enemy had done and that it was because of bobby is thats why the enemy had did it and Kc was present and heard all this and was devistated she could not forgive bobby everytime that she would see bobby she had the images of the blown up car so she couldnt bare to see bobbys face and she blamed her all the way thru it and bobby had no idea of this and wasn't at fault so kc started hating her and it hurt bobby because bobby grown to love kc as her own and felt hurt when kc lashed out at her or didnt want to see her there getting along a little better but what should kc do forgive her or hold the grudge that she is holding against her and how can she forgive bobby? So they can get along and be all happy like they used to? Just want to know your answers because I tried talking to her and I'm not really getting anywhere I know she should forgive bobby because it wasnt bobbys fault intentionally but how can she?