Dear Anika,
I was going to reply to you regarding boundary "methods" but before I did you gave me a perfect opportunity in your additional post to show you where a boundary could (should) be used for your own protection.
Incidentally, "boundary methods" was not psychological term that I picked up from anywhere, it is just my own expression for describing the action of setting boundaries with someone that is in your inner "circle".
Anyway, I don't dare tell her that her calling is getting excessive because she will withdraw from me totally and throw my insolence in my face later. Instead we are going to get an answering maching and begin screening our calls.
I think its great that you are attempting to create some space between you for protection. I ask you to reconsider on whose terms you are doing it. Are you not going out of your way now, to accomodate her excessive calling, by spending money on something you would not normally have purchased, while not actually cutting down on the phone calls? !!
What are you really accomplishing by doing this except postponing your direct contact with her?? She cannot catch you off guard as much, but you will still get floods of calls. Let me explain.
I have voice mail. Instead of discouraging my mother from making phone calls, it has given her even more of an opportunity to call with her controlling, manipulative comments and "suggestions" for day to day life - and the N's are in power because you have no voice with which to defend or stop it from! though you are not engaging in direct conversation, the poisonous words have now been allowed to be said unaddressed. No BOUNDARY has been set by hiding behind the voice mail or answering machine. You have not communicated to her that the status quo is NOT ACCEPTABLE TO YOU. They are able to ramble on and on with whatever they feel like saying, with no argument!
Eventually, I had to confront it and set the boundary - and this is what I am referring to. And it was risky, just as you surmised. You risk the spewing anger and abandonment -you used the word withdrawal- (withholding love or punishment) of her being angry that you have determined that something doesn't feel good for you. You risk the insolence being thrown in your face. But you can hold your head up high that you stood your ground and did what was best for YOU, not for her. And you can choose not to allow the insolence to touch you. It is HER insolence, not yours.
This is an example of boundary setting that worked on this very subject with my mother.
"mom, I really appreciate everything that you've been doing for me and the fact that we have been close lately. I look forward to hearing from you and talking about our week. However, I need your understanding that I am going to have to limit our phone calls to twice a week. I am having trouble focusing on the other things I have to take care of every day and am limiting my interruptions so that I am more productive. It would be very helpful if we could do this. What days would you like to talk?"
Now, mind you.... This was effective, but not without a fight. First, her knee jerk reaction was to say, "OH, I'M BOTHERING YOU NOW, that's okay I'll never call you again!!" and after a few phone calls back and forth, she managed, in a very wounded way, to accept the boundary that I had set. And, don't think I didn't feel guilty. she lives alone, and has no one else to talk to. But I stayed true to my feelings, and when she tried to manipulate me with guilt and anger, I simply kept saying (like a broken record, trying to convince myself more than her) "I'm sorry you feel that way mom. I really want us to continue a good relationship but this is the best I can do right now. I have to take care of myself."
She pouted for a week even after agreeing with my terms, and didn't call me at all. I worried about her, and that something happened to her I would feel responsible. But then I would stop myself, reminded myself that "I am not responsible for her pain". Then when I called her the following Friday (which is the day we usually spend together), I acted as nothing had happened, and said "so, what would you like to do today?" We went out that day as usual and everything with the phone calling has been fine since!!!
Anika, my relationship with my mother is far from healthy. Boundary setting is just a step, and I've only set a few, in very specific areas. But the more I practice it, the empowered I become. It is nearly impossible at first, because all of our lives we have relied on defense mechanisms to survive - REACTION instead of ACTION.
If I may be bold, I see you in me. I see, wittingly or not, that you have a little bit of a need toward your mom like I do, and so that you are afraid of embracing new behaviors to protect yourself - you are relying on your defense mechanisms that have helped you survive thus far instead. Are you reacting to her excessive calling, when you could be more pro-active? When she is calling to "check on you", is she really - or is she fullfilling her own need to be emmeshed with you?
I know what you mean about learning how to manipulate the N back. Use this skill to your advantage in your PROACTION, not REACTION. Why not say "mom, I appreciate you wanting to check on us, but let's assume that unless its an emergency, such as (give examples here, because otherwise EVERYTHING is an emergency)

we don't really need to check on each other, right?". Make her feel like its partly her decision, and at the same time you are setting YOUR BOUNDARY.
I don't know if this will work for you - but I bet if you tried, you would be surprised. I am not an expert, but you asked me about boundary setting and this is what I've learned, in therapy, and it seems to be working fairly well as long as I stick to it.
You said you are more empowered now with your knowledge - absolutely true. Can you take it a step further, and use this power to ASK FOR WHAT YOU NEED?
You are in my thoughts. Good luck.