He had mentioned Elizabeth's reactions, and then announced that he couldn't, with their current state of equipment, follow her without alerting her. Elizabeth couldn't get a good enough mental lock on to track her, and if he was following, she would realize it and react. He was not a stealth operative, he needed Ghost for that, and she was likely grooming her tails, or being a Fae and too busy to interact with mere mortals, or the area was too familiar to the target, or some other pissy excuse for why her illusions were not required for this operation. Instead, they would be alert for her at a later date, and turned off, heading back to base rather than attempt a possible conflict with his powers in an unreliable state.