you need to get into the room that's located at the end of the control room (where you deactivate blue and green MQ), you will need scissors.
after you get into the room, you will see a camera of Black MQ dancing with the other two, the timer will go down and she will come to you.
On a side note, it seems like unlike the other two, if you look at her, she still runs at you... lowky scared me