I’m a big guy a bit over 6 feet, but my wife is way better at fixing cars than I am. I can change a tire or the oil or other very basic stuff. But she can make actual repairs, like adjusting timing belt, mount a tow bar, change a ball joint. Where afterwards things actually pass safety check which is mandatory in Denmark.
I’ve even been complimented by mechanics for her work, because I’m always the one driving our cars to check afterwards.
I would NEVER have a problem with a woman fixing my car. On the contrary I bet a female mechanic has had to prove herself more than most, so I’m guessing chances are higher that a female mechanic is actually pretty good.