sorry, i got to this thread a bit late
is it possible for you to locate her by phone (find my iphone, or similar for android/win-mo)

had a bad experience last year of trying to track a family member. we located the phone, alerted police and the perpetrators were caught and body excavated (won't say anything further, too sad a story).

point is, you may be able to trace the phone's location (before police took over) and accessed its pictures gallery for clues. i and a couple of other family member did this.