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. The tissue needs time to accomodate to the impact forces of running.
Patience is a virtue.