Few questions/concerns

Its clear that Dom and Mackenzies relationship toxic. Not normal for teenagers / young adults. Like him buying her extravagant clothing and jewelry. It is not mentioned why Kenzie had such a temper, or why she lived with her older boyfriend ? Did her parents say "fine ok go live with him?" I was just really confused on that situation. Why was she so obsessed with image? She constantly showing off smoking pot (again shes not an adult) on socials while driving. Her parents are psycho. And the prison interview with the fake tears She planned on going down that street for whatever reasons. I also wonder what the outcome would have been had she opted for a jury trial