Mark 5:42,43

‘And they were immediately filled with great amazement (amazed with a great amazement), and He gave them strict instructions (charged them much) that no man should know this.'

This counters all arguments that Jesus knew that the girl had not really been dead. Jesus did not try to explain to them that really she had not been dead at all. He told them very firmly that no one must be told that He had raised her from the dead. There is not even a hint that He tried to explain otherwise, and Peter was there, so he knew. Jesus did not want the news spreading because he knew what the effects would be. He could not go around restoring everyone who was dead. Had the girl only been healed there would not have been so much cause for their remaining quiet. All knew that He performed healings.

The extreme amazement was to be expected, evidence that they certainly thought the girl was dead. The remainder not so expected, although it fits in with Jesus general attitude elsewhere. He did not want to excite the easily excitable populace.