As I understand it (there are several variations that I've heard), she was taking the horse she was using down to the stall area from the outdoor ring when her horse slipped on the gravel and somehow went down with her. She hit her head on the pavement and the horse went down on top of her. Special prayer for her and especially her family.
We were discussing this over the weekend and I don't understand why riders under a certain age aren't required to wear helmets. She was hurt pretty bad by the horse but would have probably survived except for the head trauma.