I also believe that, in her own way, your mother loves you, too, but perhaps, too much, in a sense. While I have seen situations that are similar to yours concerning mothers and daughters, I must say that your mother has apparently assumed a great deal of control in, and over, your life. The tone of your letter indicates that you are becoming understandably irritated with your relationship with her and you seem to have reached a point where you are ready to make some changes. From what you have described, I believe that this is a very good idea. Your mother could very well be the type of person that simply feels the need to control not only herself, but the people around her.
Some people are just that way.
Her insistence on ensuring that she not only has some influence, but also some control, over your children, supports my point. She is apparently not simply acting in the capacity of a grandparent, she is, at times, assuming your role as the parent of your children. By doing this, she is both fulfilling her own 'need to be needed' and inadvertently sending a message to you that you in some way still need her help. I am in no way defending your mother's behavior. Rather, I see her as a woman who is having great difficulty in accepting the idea that her children no longer need her as they once did.