OK, so this helps me a lot. The left right brain body connection is usually fully formed around six or seven years old. What you’re describing is called “open-chain intolerance”. Rotation is excitatory to the brain, where strait lines are calming. So usually when I deal with this in a child, I will ask the child not to attempt the skill on their own, but to hold a nice tight shape, and I will rotate them around the bar slowly. I do this to build confidence for them. I will also put a very high mat in front of them, and let them use their feet to crawl up the mat and kick themselves over. Having their feet on the mat means more towards the closed chain tolerance, which reduces the anxiety. Having the feet on the mat all the way until rotation, builds confidence.
It’s not uncommon, and certainly not something that can’t be overcome. I wouldn’t wait too long to work on it. I also suggest working on this without other kids waiting in line watching her if there’s too much stimulus or pressure watching her then rotation is only going to add to that stimulus. Gymnastics is a mental sport before it’s a physical sport no matter what age you are. If it were a kid I was coaching I would do maybe one or two privates with her to work on this specifically without it being a class environment and I wouldn’t make a big deal about it. Also, if the gym offers open gym, letting her free play with this is good as well.
I hope that helps. Feel free to ask me any more questions. I will do my best to answer or help out where I can.