Question

1. She helped it happen for me to drive a car.

2. He let it happen to break the window.

(What about these sentences? Can we use these structure?)

Answer 1

These, too, are quite awkward and the phrasing would not be used. Try these instead:

1. I wanted to drive a car, and she helped make it happen.

2. He didn't stop the children from playing ball in the street, and they broke the neighbor's window.