What a beautiful horse and she decided to take a photo, trying to avoid the sign showing that this is a real electric fence in the capture. She took a step for a better photo, and her feet were no longer attached to her legs. It was the last photo in the camera for the day. As she was falling she gripped the wire to stop her. A tingling sensation travelled through her arm, she immediately released her grip on the wire and fell. And the horse just stood there and wondered what the stupid humans would do next.
Based on an experience made by me a couple of years ago. Never grip a wire when falling, you never know.