You're relationship with your mother sounds very much like that with mine. I think that you have identified the nature of the problem, but it's very hard to break the cycle. In my view you have to make a step change, i.e. something abrupt. My advise is reduce the frequency of your calls. Give her clear signs that you are independent and deserve your own space. Probably she will increase the pressure on you and make you feel very bad about doing this, but in the end it will be better for you both... I say that as someone who is in the midst of trying the same tactic with my own parents, lol.