I would take it at fact value; your mind is interesting. It sounds like you have a bit of trouble with self-worth issues, don't think much of yourself, mind, intelligence, abilities, reasons for being in therapy?

You are your mind as well as all the rest of you; you cannot divide out the way you think, categorize, imagine things from "you". If she had said, "that's what makes you so interesting" you would have had to say, "What does?" as "that" and "you" are too general. Because she made one of them more specific, your "mind" you were able to assign the way you were thinking to your uniqueness.

It's a bit similar to, "you have nice large eyes, that's what helps make your face so expressive". You are you is all she was pointing out and, since it's therapy and you all are just talking/using your minds and hearts but not "doing" anything, how you think/express yourself will show up more than something else might. It's not positive or negative really, it just is (in her opinion).