There is a certain point in a child's life where they are either going to hear it from you or hear it from a surgeon. My 11 year old had a desire to jump from high places for a time as well. He bruised his heel once and had a hard time walking for a week. Pain is a very good educator. Dissuade them from anything that may end their short life early, but if it's just going to hurt, let them go. My guidance for kids generally is to be mindful not to tear up the furniture or harm others, but if this hurts after I've warned you it's on you. Here is the first-aid kit. We ultimately got them a trampoline, which was extensively used.

You dont convince her to stop you encourage it. There are places you can go so she can jump to her hearts content. If you cant afford it build her a living room obstacle course with the couches and pillows. She will need to follow your rules to get all of this. Too often we kill our kids dreams with out knowing it.

Get her to a kids gym, they'll teach her how to land safely at least. I haven't done gymnastics for 30 years but when i go for a sixer i still auto roll to minimise injury.