I'm more surprised that she was able to drive at 8. This was long before they had power steering, and it takes a good deal of strength even nowadays having lighter weight vehicles to drive a car without it. She must have been a very muscular child, I'm guessing from farm work.
What to address first....
There were a broad range of cars until maybe about the 1940s. They were aimmed at a varity of people. Blah blah blah. There were many cars made for women. Some of the Women Cars only drove a few miles per hour and could be entirely operated with one (weak) hand.
The line cars were cheaper and easier to fix, upgrade, and replace things on so those became more popular. The popular.. cheaper... cars... were heavier and harder to steerxp The weight changed and junk, too. Remember some cars had wood wheels. The monsters of the 50's would can crushed those in no time. Pre-1940's it's the starting a car that was difficult.
I am not shocked she could drive at 8. Firstly, she lived on a farm and everyone in a family of farmers is equally important and must be able to take over in an emergency. Secondly,.. the time period.... was normal for kids to find some dumb car owners ( usually rich brats) that would let kids play with ( actually drive around unsupervised) their car. But cars over piled with children became the top way a person could be killed by a car. Third, you could make up your age anyways.
She probably had to get her liscence so she could regularly drive things to make up for the absense of her father on the farm. Both to move things on the farm and to transport products.