"She bounced off, went flying at least three metres in the air and was thrown clean over the top of my car," Ms Hegh said.
Grace was unconscious and motionless for about a minute before she started to make "a gurgling sound", her mother said.
Drifting in and out of consciousness, Grace woke in the ambulance on its way to hospital and asked if "everyone was all right".
"That's just typical of our girl," Ms Hegh said. "She's the kind of kid who draws others to her because she's caring and warm. At the hospital she was apologising to the nurses and other staff for causing such a drama when they were already busy."
The "drama" left the charismatic young entertainer with an egg-sized lump on her head, a black eye, stitches, abrasions and extensive bruising, but miraculously no broken bones. It will take time for her abraded skin to heal and, in the aftermath of the head injury, there will be no bouncing for a while.
Saturday's fundraiser - which included a garage sale, barbecue, cake stall, cheerleading and hip-hop dance displays - was being wound up at about 2.30pm because of the increasing wind when the accident happened.
The up-and-coming cheerleader needs to raise $10,000 get to the All Stars event in the USA in April, after being scouted by top American choreographer Luke Johnson.
A fundraising auction has been postponed until Grace is well enough to resume her cheerleading passion, Ms Hegh said.
"We're not even thinking about that right now. We've got our beautiful daughter, she's alive and she's doing miraculously well. She really is our 'Amazing Grace'."