I think it is important to understand Disney is not as safe as one would think. Unfortunitly I learned the hard way. My daughter was violated at Disney. She was taught how to handle situations. She did not respond in the way I would expect. She said she was having a hard time processing what was happening and what to do. It was while she was on the Stitch ride. I was there with her one seat away, and she was sitting by her baby sister. It was during the dark part of the ride. I learned the hard way that Disney is not seperate from the world and predators lurk everywhere. We reported it immediately and police were called. The police officer informed me it happens more then one would think at Disney. She gave a discription of the guy but they were un able to locate him on the cameras. It isn't so much about a nine year old and if she can handle it, but more about the sick people realizing she's sitting alone.
It makes me sick to think not only did this wacko get away with it, but that another family may also learn that even the happiest place on earth can have a dark side.
Maybe you could offer a deal with her to try a ride and you can reward her with something special. Watch videos before hand to reassure her it's ok. I would not recommend leaving her alone anywhere in Disney at 9 alone.
My sympathies to your daughter! That must have been very upsetting to you all.
The fact is, a child, teenager or adult can be touched inappropriately anywhere at any time, even if you are by their side 24/7. My daughter started riding the public city bus to school when she was in grade nine, and we practiced saying, "HEY!" really loud if ever she felt a hand go where a hand don't belong. I emphasized to her that she would feel shock and confusion, and the best way to deal is to channel it all into a nice loud exclamation. The only person who will be embarrassed is the person touching you inappropriately. We roleplayed this several times.
I knew she could make it work, because she had already got cornered once in a grocery store when she was nine, running an errand for me. The man was crowding up behind her when she was looking at something on a shelf, and when she turned around, he stepped even closer (almost touching) and leered at her. So she looked up at him and said, "EXCUSE ME! Can I HELP you?"

Apparently she was so loud, he jumped back and everyone around turned to stare at him. He retreated quickly and my daughter finished her shopping and came home with her feathers a bit ruffled, but otherwise pleased with herself.
Btw, I'm curious, since I've ridden Stitch several times... It's only dark for a moment, and everyone is locked into their individual seats. Did this person somehow get out of their seat, or were they seated next to your daughter and reached over? Being grabbed in the dark must have been terrifying, poor kid.
As far as the OP goes... yes, I would absolutely have allowed my kids at nine to exit at the chicken exit and wait for me at the end of the ride. That's assuming, of course, that we'd gone to look at the exit together already. If they had a cellphone, even better. I let my son go to Disney with a friend's family when he was 11. While he was there, he and a nine year old girl got separated from their group. They asked a nearby castmember for help and were shortly reunited with their adults. As long as any nine year old in my care was capable of at least that much, then I wouldn't worry about letting them out of my sight for a few minutes.
(That said, I WAS a bit uncomfortable letting my seven and nine year olds roam Tom Sawyer Island on their own, on our first trip. It was all new, and there were dark tunnels, and for some reason I was sure they were going to get lost and, I dunno... kidnapped by pirates or something. The next trip, at nine and eleven, I was much more relaxed and just told them to stick together.)