No she doesn't have a cell phone. She and her sister text-messaged the bill sky-high, and the account has been inactivated. You can bet that will be fixed tomorrow though!
Does she have a credit card or a gas card?
Does her sister have any ideas? Also, was she driving her own car or is someone else her usual transportation? Any new boyfriends on the scene? I have been through this before with my sons and literally, had someone watch the phone at home while I drove their usual routes to their usual haunts looking for their cars.
Also, Young Life has adult advisers who might be aware of people she was hanging out with when they last saw her.