If the disruption was really as minor as taking out her phone, that could be reasonable.
In a more general case, you could easily have a kid who wouldn't stop talking, watching videos, whatever form of disruption. Some kids will do it just to be assholes (or regain some missing sense of power and control in their lives, etc, etc). I don't think you could realistically just let them ruin a class period for all the other students. If nothing else, it would totally invalidate the teacher's authority. You get some kid with oppositional defiant disorder and you're going to have a bad time if you give them an inch.