Once Charles was close enough to define any discernible features, he immediately recognized who she was and could put a name to the face, as he would have done any of the children who were so integral to the island - albeit only knowing in a second-hand capacity. He also knew who her parents were, to whom he made a mental note to inquire as to whether they considered it wholly appropriate to let their daughter be out so late in such a place.
Especially when he knew exactly what that distinct smell lingering in the air above her was (though he would not be sharing with anyone his personal experience of how he knew that). While the effect of what recreational drugs could do to a subject was a potentially untapped source of research, this was not what he would have called a valid situation for evaluation.
Despite that, her actions were curious; clearly alert enough to sit up and look straight at him, but followed with a lingering pause, some lost moment in herself when he might as well not even be there. Call it instinct refined by years of observing people, but that did not strike him as entirely normal.
"Perhaps there's something I've missed, but is sleeping out on the beach a new trend I haven't heard about?"