Had your friend just washed their hands when you tested him / her? I had a similar thing with my mother, when she saw me testing my BG she asked if I would test hers.
"Clean hands?" I asked
"Just washed them" was the reply.
I duly did the test and it was 22.0! Horrified, I did another which was not much better.
"Have you eaten anything sugary recently?" I asked.
"Well I've had some dates..." was the reply.
She washed her hands and I tested again and she was text book normal.
I would be sure that your friend had not been handling anything that could give a high result. If this is not the case, I suggest that you ask them to see their GP and explain what happened.