Walk her out.

"Take her out the front." You tell the guard, and use your power on the rest of the staff to allow him to do so, unquestioned.

You get to the visitors car park and see, what is clearly a mafia member parking a convertible two-seater. "Hey you, give me your keys, I'm taking your car." You yell to him.

"Sure thing, chief." He says, tossing you the keys. You enter the car and move it around to the front gate to wait for Harley. Soon the guard escorts her out the gate and lets her go. Harley jumps into the passengers seat of your new car.

"Alright Boss, what now?" She asks, still not entirely happy with the arrangement.