They’re probably afraid that she is trying to injure herself and then she will sue them.
This is a legitimate concern, and I don't blame the board members for insisting that she stop. If she gets hurt at one of these meetings, there will be a stampede of lawyers willing to represent her in a lawsuit. Okay, it's great that she's able to do a cartwheel at her age, and it may be cute and all that, but why in the world does she need to do them at this type of meeting?