So his greeting wasn't the friendliest of ones, but he wasn't exactly in the mood to be cheerful and when she stepped back he couldn't really care about how she felt about it, except why should she be angry? She just used her powers and took a peek into his head without permission. He should be the angry one, and he was.
John hated when telepaths did that, it was an invasion of privacy, and they had no right to use their powers for snooping around. It didn't make him feel any better, in fact it just pissed him off more. "You show up unexpected after I arrive so who do you think I'm going to accuse? And you had no right reading my mind! I left that school because, believe it or not, I had no friends anymore, not after what I did and besides Magneto taught me more then Xavier ever did."