Jingbo Steering Lock / Anti-theft lock for all cars (Universal).
You might try a little education first: explain that her efforts are a waste of time and energy.
The steering will lock anyway should anyone try to move the car without the key in the ignition. Any movement of the steering mechanism, whether at the wheel or the front tires when the key has been removed, will release a spring-loaded lever – causing it to engage a slot and lock the mechanism. That is what is happening when she moves the wheel.
That, added to the strain she puts on the system, I suppose, could eventually create some wear on the locking mechanism.
My dad followed the same practice. We lived in a fairly rural area where there were no taxis, let alone public transportation, and the car was essential for him to get to work. Only later did I realize the folly, and cost, of that scheduled trade-in approach.
I can recall four cars we owned during my years at home. All “factory-recommended” service was performed by the dealer on schedule and there was never a single major repair issue, so perhaps he was on to something. But there was a reason for the lengthy list of folks waiting for his trade-in.