The instructions given to her had been fairly clear; Chell was ill and it was suddenly GLaDOS's responsibility to do something about it. Though it really wasn't her problem, she didn't have a choice in the matter. But, then again, surely it wouldn't be too bad. She couldn't cause much trouble if she was sick, and she was smart enough to know that it would be counter productive to attack the person trying to help her, anyway.
The only real question left was where exactly the girl was. If GLaDOS was lucky, she'd still be in the facility somewhere. If she had left again, tracking her down was going to be a lot harder. So, hoping for the best, the android began scanning through her camera feeds in search of the missing girl.