I was about her same age (19), when I drove one day with head phones on (music playing loudly). I was barely able to skid to a stop just as a train was coming through. By the time I stopped the train was right in front of me. There were no gates, just a sign about the train crossing (which of course I paid no attention to). I never drove with headphones on again and am extemely cautious when approaching train tracks. It scared the crap out of me and was something I have never forgotten about.
I can't imagine why someone would jog on the tracks, but teens are notorious for their lack of judgement and the attitude that "it won't happen to me".