Hey piggy, My grandmother was exactly the same when I lived with her, and she still calss me all the time to make sure I'm eating right, have enough money etc etc.
I don't know why she is the way she is, but here's my theory...
My Grandmother had 4 kids, all boys, so I was like the daughter she never had, also, I think that it made her feel like she was needed again, since her boys had long since left home.
Besides looking after you, what other things does your grandmother have in her life? Does she have much of a social life? hobbies?
Maybe she thinks that if you think that you need her around, you'll keep living with her, so she's clinging to you.
Just a thought, hope it helps.