My mother won't grow up!

My mother is 51 years old. She acts like she’s about 12. No, really. It’s not just that I’m mad at her right now, she does it all the time. She makes me late for school every day because she refuses to wake up until 10 minutes before we would have to leave to get to school on time. Her mother (my grandmother) comes up all of the time and does the dishes, laundry, and cleaning. She also cooks us dinner 3-4 nights a week. All the while my mother is usually napping or acting like she’s sick so she doesn’t have to do anything. She always goes on and on about how I should help, and I want to. The problem is that I cannot clean our entire house and do everything by myself, and she won’t help. She wont teach me how to do laundry or use or vaccum. (Please don’t think I’m stupid, I know how to use a regular sweeper, but we have one of those really complicated ones from Rainbow that require assembly and such.) She also waits until the last minute to get ready for anything, which means I’m always late to birthday parties, school events, and practices. If I try to conront her, she starts complaining that I’m attacking her and saying she’s a bad mom. It’s so embarassing when my friends come over and the place is a mess, because eventhough I’ve cleaned for hours, it’s just too much for me to do alone. I just want a mother who is just that- a mother- instead of a whiny 180 pound baby. How can I get her to grow up without making her mad??