She has a reputation that 'commands' attention/respect. [=people give her respect/attention because of her reputation]
In the United States, the President as the commander in chief is at the head of the military 'chain of command'.
She seems to be 'in (full) command of' the situation. [=she seems to have complete control of the situation]
(..) In hours this ship has to be launched. Geordi, the ship was damaged in the attack. Get a repair crew down here. I'm on my way. Alpha team, we're heading down to the surface. Porter, take command while I'm gone. Check out the environmental controls. It's a little warm in here. Isn't it amazing? (..)1996 Star Trek: First Contact
(..) I am reading fluctuations in their power grid. Number One, open a channel to the fleet. This is Capt Picard. I'm taking command of the fleet. Plot in the following coordinates. Fire on my command. - Is that a vital system? - Trust me, Data. The fleet has responded, sir, they're standing by. Fire. (..)1996 Star Trek: First Contact