As soon as the battle starts, the ghost will somewhat slowly come towards you and try to attack you with her scissors. Try taking a photo of her as she is doing this for a relatively easy first hit. As soon as she gets hit, she will vanish for a few seconds.
After this, the ghost will pop up from any of the walls and charge towards you. In order to see her coming, keep rotating the camera and running back and forth near the middle of the room. Try to stay away from the walls.
As soon as you spot the ghost attacking you, start walking away from her backwards and pull up your camera to take a photo of her as you do so. This should be relatively doable as she's not too fast during this battle phase.
It should take about 3-5 photos to trigger the second phase of the fight.