Artist's description from DA:When news of the First Great war first broke out Fluttershy was training to become a full blown veterinarian. But when the draft rolled through she had to make the transition from vet school to med school. And while med school was a good confidence booster for Flutters as she began to meet other ponies who were drafted, she was terrified of the front line. carted overseas and dropped off in Zebrica, Flutters was assigned to a MASH (Mobile Army Surgical Hospital). At first it was excruciating but over time Fluttershy grew numb. Not to her patients, but to the constant gunfire and bombing. She stayed vigilant sure, but it no longer spooked her and made her want to hide under a table. It hardly made her blink.
When she finally made it home she was tired and cold to the world around her. It took some time, but eventually the old Flutters started to come back. but just a bit. She was warm and smiling again with a soft sweet voice, but she no longer was startled easily. Nor did she feel the need to treat animals. She found that she preferred it when the patient wasn't driven by instinct and could do as you asked without sedative or large food bribes. Ponies and other creatures just wanted to get better. She returned to med school and finished her PhD. Shortly before her wedding she opened her own Clinic for General and Public health.