There will be no way for her to join you at that time of night. My suggestion would be for her to spend the night in her car in the transit lot and catch the first shuttle bus into the park the next morning. I believe the first bus leaves around 5:30 or 6:00 a.m. She wont be able to drive her car to TEK and you will not be allowed to drive to the gate to,pick her up. Riding the bus is her only way to get from the main gate to TEK.
You can go on the park's webpage and pull up bus schedules a couple weeks prior to her arrival.
Do you know about the free shuttle bus rides for TEK campers? Definitely one of the best bargains in the park.