That's quite a conundrum. I know it would be hard to do, but maybe you can nicely point out to her how she does it all of the time, and how it bothers you. If she is a real friend, she will understand. If you do invite her over for dinner, ask her to help with the cleanup. I know that she should automatically be considerate and insist on cleaning the dishes, but it appears that unless she is asked to help, she will just assume you will continue to do it like always.
In regards to the latest situation tonight of her saying that she will bring dessert, tell her that Dessert would be nice, and you will be sure to have a pot of coffee ready to have with it (no dinner). You should not have to make a whole dinner for her and her kid if you don't want to. A real friend would not assume that you will cook for her/him anyways.
If she feels offended, or puts up a fuss, it will show that she is just a user and not your real friend. Friendships and relationships are give and take, and it seems that she is quick to take, but not interested in giving anything in return.