I talk to my T in my head all the time... Before my T I would do it with my best friend, before that with random people or a teacher or whoever I felt like talking to. I don't think talking to someone in your head means that you are not facing your issues or thinking about yourself. For me for example it is much easier to think about myself if I imagine a conversation, instead of just sitting there going 'why is this like that'. Also, in thinking about what you'd like to tell your T during a session, aren't you actually thinking about yourself? You are thinking about what you deem important in your life, what bothers you, what you want to improve on. As others have said, this happens to a lot of people. For some it gets 'better' over time as they start to move away from that dialogue and towards talking to themselves or another person in their life. For some it will always be their T to whom they talk on some level (or rather who they hear as a voice to guide them in life), as far as I have heard.

As you have already said yourself, the most useful way to resolve this for yourself is to talk to your T about it. She can change things about your therapy so it moves into the direction you'd like it to.