You don't need to go to Pamplona to get to St. Jean Pied de Port.
Talk to a travel agent about a train from Madrid up to Hendaye on the border with France and on to Bayonne and finally SJPP. In 2004 I connected with some pilgrims who made the whole trip from Madrid to SJPP on the train in one day.
I would only go through Pamplona is I was starting in Roncesvalles, but I really recommend starting in SJPP. The walk from SJPP over the Pyrenees on the first day is talked about with all the pilgrims you meet on the rest of the Camino. "Where did you start? SJPP you say, how was your first day?" It is always memorable.
Teen girls will have a terrific time with other young people on the Camino. And it is very safe if they use common sense.
Buen Camino,
David, Victoria, Canada.