Once Chell is down and set up the light bridge, GLaDOS sets up the new batch of portals and sets up the cube so that it will redirect the laser onto the device and unlock the door. After that, it's a simple matter of letting the reflector cube go its way on the gravity emitter.

Once that's all well and good, GLaDOS makes her way to the elevator and folds her arms across her chest, waiting for Chell to catch up and for the lift to move.