Make 'seeing' someone's thoughts very, very complicated. People don't usually think the same way they talk. It's a whole mishmash of thoughts, other thoughts, subconcsious thoughts, emotions, images, sounds and feellings.
If you really want to mess things up introduce some Freudian psychology. One character may 'see' that the other has a Oedipus complex or relate her with his mother. Of course, the one being mind read has no idea at all as it's a deeply buried process.
One person may have a song stuck in their head.