Medicinal marijuana is legal for the treatment of PTSD in New Mexico, but I think prescription medication coupled with therapy is the way to go. Different people respond differently to medications, so it may take a while to find the right medicine or combination that works for your daughter. I have found that therapy and medication management has lead to greatly decreased intensity of symptoms.
For some of us PTSD can be life-long....however, it can still be managed and isn't necessarily a "death sentence". I would recommend that she see a trained trauma therapist and a psychiatrist, as opposed to a regular MD.
For the record, I take Celexa , low-dose Abilify, and Prazosin and couple that with cognitive-behavioral therapy.