Keep in mind though that if she's not dealt with the factors that caused the stress fracture in the first place that she's likely to have a return of symptoms no matter how conservatively she resumes training. Strength issues - primarily hip strength, but also hamstrings and quads. A gait analysis may be a good idea, if for no other reason than to rule out the biomechanical stuff and to make sure her shoes are correct for her feet. Also keep in mind that if she has a leg length discrepancy that this may play a role. The tissue needs time to accomodate to the impact forces of running.
Patience is a virtue.
Some of the factors to consider when looking at the cause for the stress fracture include - flexibility issues, strength issues, biomechanical issues, and training errors. How she gets back into running is crucial. Though she's probably been able to cross train during her time off running, those things don't stress the bone and muscle the same way as running does. Keep in mind though that if she's not dealt with the factors that caused the stress fracture in the first place that she's likely to have a return of symptoms no matter how conservatively she resumes training. A gait analysis may be a good idea, if for no other reason than to rule out the biomechanical stuff and to make sure her shoes are correct for her feet.