Maybe instead of telling her that she doesn't know you as well as she thinks she does, you can suggest that the two of you share some time to really talk about things, without the assumption that you know everything about who the other person is. Acknowledge that many times with a long term relationship, we stop really seeing the other person and start taking shortcuts and putting them in boxes and don't see them changing and adapting, or don't see that we put them in the wrong box.
There's a few really cool party games that basically have random questions that you choose and answer, and it starts conversation. I can't for the life of me remember the name of it, but seriously... it might be a fun evening for the two of you to talk about new things or old things with new perspectives. Like NYCindie said, it's great that there is still more to learn, time to capitalize on it and use that to build new ties and bridges.
I'm actually going to steal this idea for when hubby comes home because we definitely have that issue as well. He hasn't really seen ME in a long time, and I still see him in terms of old issues and problems. We really do have to sit down and meet each other all over again.