Legal Question in Personal Injury in California

I would say that if the equipment were neither defective nor unsafe, and was being used as intended, it's the risk the parent and child take. I hope that your daughter is doing better now. I'm sure she hates the cast!

It depends on who was at fault. Was the equipment defective? What was put underneath the equipment and by whom? If she landed on a landing area that was unsafe, there may be a claim against who installed it. Who was watching your daughter when she fell? Should she has been using this equipment? You may have a claim againt your sister in law, but if she has no homeowner's insurance, you would be going against her personally.