Her back foot caught on the lip of the doorway, and she stumbled.
Have her point her toe to the camera and place her weight on her back foot.
Next, have her point her front foot forward, so it is at the 12 o'clock position while the back foot is placed at the 3 o'clock position.
Pushing against a wall, stepping forward while leaving the back foot flat on the floor.
Bring the front foot in fourth back to the back foot and try to achieve two parallel lines with your feet.