Nursing a changeling is like nursing an animal: give it bandages, feed it, take care of it, and when it's better, let it go. Fluttershy knew that it was dangerous, knew that if she got caught, then her life was over. Off to the dungeons she would go. Yet, she couldn't help it, seeing the poor, mangled creature at her own front door. So she took him in, hid him from the watchful eyes of the other ponies. Eventually, what began as an effort to help another creature, blossoms into much, much more then simply a relationship of nurse and patient.