It would be by no means difficult to do as told, and staying in her spirit form would indeed be a good idea. She had slight hopes he would have told her to stay as she was though. It was a very different sensation, and she didn’t quite like the feeling of not being fully there. Without a complaint though the Lancer listened to her Lord, and disappeared, taking on the form that could not normally be seen or felt by those who weren’t servants or the Master of one.
“Then let us depart. I believe the saying is that Time is of the Essence? Or something to that effect. I presume you don’t want to waste any time after all, and swift victory would be your preference?” Asking the question which was semi-rhetorical, she prepared herself as she was to get moving. If anything this just meant she’d have to be ready to take her materialized form at a moment’s notice in case something happened. Without her headband or waist guard though, as both would immediately give away her identity to anyone familiar with Japanese History. While fame had its uses, it also was very inconvenient.
Though in the long run it may work out. IF anyone figured out her identity, that would probably paint them as the very first target in this war. Then her Lord would give her someone to fight, and she would be able to prove how powerful she was to him. If something happened she could show off, if nothing happened then peace of mind would be obtained. No matter what, she saw this as a winning situation.