"Take your kids to the elementary school this weekend, pack them all up with their book bag, their lunchbox, cute little back-to-school outfit, their new shoes - all the works - and go take a tripod to that elementary school, junior high, high school ... and go take the back-to-school pictures on the weekends."
You can be proactive about this and you can make a plan for de-escalation if your prophylactic measures fail. Mother and daughter being close is a wonderful thing. Being 'prone to fighting' is not.
The question raises concerns about the impact of a smartphone on children's friendships, especially when one child doesn't have a phone, and offers advice on how to manage this situation.