Since your T was asking in such a non judgmental way, you could always tell her that she's fantastically intuitive sometimes, and that you've never lied to her before so you wanted to correct something. She asked a question that you weren't ready to discuss and it caught you off guard and so you denied it, but you still don't feel ready to say anything further about it. You just wanted to make sure you hadn't been dishonest with her, and you could leave it at that.