In the US yes she was assaulted - if an adult touches a minor in that way the very least it is is sex abuse. The guy could and should be criminally charged if she reported the incident to police. Minor does not have a duty to say no. Adult simply cannnot touch the minor - black letter law in most if no all states. Add the authourity figure issue and the guy is in real trouble. Tell your friend to stay away from him and report the incident.