You need to sit down and have a little conversation with your mother, or hon, you are just doomed. She'll do this the rest of your life.
When you observe that Mom's behaviors are inappropriate, you need to lovingly, patiently call her on it. Just say, "Mom, that is inappropriate." Practice in the mirror so the rush isn't so bad when you finally say it.
For example, when she demands you have dinner at home and then demands that you cannot leave, and you let her know you are going out for dessert and she basically assumes your decision making, you need to say, "That's really not appropriate, Mom, and I've decided to go over for dessert."
Repeat as necessary, give her a kiss, and go on your merry way.