How to Enforce Boundaries With Mom?

Regarding your mom's texts and cards, just wait it out.  As for your sister, just keep repeating the same mantra "I don't want her in my life," "I can't handle the drama," or whatever it is. Pick one short, simple explanation and just repeat it, without regard to what your sister's argument is. "But she's your mother!""I don't want her in my life."  "You'll never forgive yourself if she dies and you didn't have a chance to reconcile." "I don't want her in my life."  Etc.  

I agree with the previous poster about just ignoring/waiting out your mom. (and agree she sounds like a real piece of work) However, the relationship with your sister is the one you need to perhaps put more effort into preserving. I suggest you two have a sitdown (or scheduled phone call if she's not local), where you take it from the top one more time about why you don't want your mom in your life, but discuss how you two will remain in each other's lives despite the mom estrangement. Keep in mind she might be under a lot of pressure from your mom to take sides or heal the breach. She also may be worried you plan to stick her with the whole burden of eldercare when your mom can no longer take care of herself. (Do you? It's time to think this through.) You and she will be living a lot longer than your mom; no matter how much drama your mom tries to create, don't put your sister in the middle of it since that's an ugly place to be.

Good for you for having given it a second shot. That said, sounds to me like your mom is toxic. Mine was as well. I didn't hate her, but decided I would be happier (and by proxy, so would my children) without her. She passed away this year. My siblings had stayed in touch with her, but I kept her out of my life for the last 25 years, and have no regrets. YMMV, and perhaps I'm projecting, but it sounds like you know what you need to do. Your and your sister each have the right to define your own relationships.

The ages are a little off, but if I didn't know better, I'd swear one of my sisters posted this!  Pretty similar circumstances but my mother is widowed and my middle sister, my mother's favorite (yes, she unabashedly told us that) died about seven years ago.  My mother, like yours, used us sisters against one another to be the center of attention and to cause us all to do the "pick me dance". Both my older sister and I refuse to dance any longer.  My sister lives out of state and sees Mom on her own terms, usually a short trip where she stays in a B&B and visits for a meal and a short time.  My sister has told me that some days are fine and others, Mom has talked herself into a fit, so their conversations or visits are short. My sister leaves or hangs up if Mom becomes hostile.  

Part 2 and sorry this has turned into such a novella!

FWIW, my sister and I get along fine, but we're not particularly close due to a large age difference and the fact that she's lived far away since leaving for college.  However if something were to happen that she needed my help, I'd be on a plane in an instant to help her.    Perhaps you can talk to your sister and let her know that you're there for her, but you refuse to talk about your mom?  That way you two could have a decent relationship independent of your mother's drama.  

To another poster's point, once your mother's health begins to decline, you'll want to have some modicum of trust so you can handle your mother's affairs amicably. I speak from experience because I am local, and therefore responsible for my mother's long term care.  She is close to 90, has progressing dementia, but otherwise is in pretty good shape, healthwise.  I do have power of attorney to manage finances, etc. but that was a battle because: a) I had to take her to a neurologist to get an official diagnosis that she has severe dementia (she thinks she's better off than she is, since her overall health is OK); and, b) I had to have a side conversation with her lawyer, show him the diagnosis and have him convince her that she really should put the POA in motion.  She kept insisting that I only needed to "help out".  I found out that she wasn't managing day to day finances very well and nearly lost her rights to Dad's pension, lost bills, didn't pay taxes,etc.   So I went nuclear and had all her mail forwarded to me, contacted everyone and made a zillion copies of the POA to let them know that I was now their contact person.   It was a two year process, and I think I've found all her retirement and benefit accounts, but because she wouldn't share the info freely with me, I may be missing some things.  Long story short, she is now permanently mad at me because I "took over without her permission".  She has accused me of lying to doctors, the lawyer, the staff at her assisted living facility, you name it.  Ironically, it was my older sister that gave me the best advice ever:  just step back and let her talk.  They'll see the cra-cra for themselves.  This has helped me let some of her shenanigans roll off my back.  I share information with my sister on accounts, expenses, etc. so she is aware and there are no hard feelings about how the money is being spent.  

But do I visit her?  Rarely.  On Mother's Day, my son and I took her flowers.  We stop in on Christmas and her birthday.  But my son does all the talking and we're in an out in half an hour or so.  Sad, but made.bed.lie.

Last point, you may want to read up on Borderline Personality Disorder.  I had a very helpful therapist recommend I research it after I had described my mom and my relationship with her.  Several ahha moments, let me tell you!  It, too, was helpful to manage my reactions to my mother's often hurtful words and actions.

Your mother and your sister can't control you. They have no say over what you choose to do or whom you choose to have close to you. You can block your mom from texting you. Abusers LOVE postcards because you can't avoid seeing them when they arrive, even if you try not to look. That is a classic move. With your sister, well, she can back off and leave you to your relationship with your mom or she can be estranged too. It is okay to do this. You don't deserve this treatment. It doesn't matter what they say to anyone -- you put yourself first. You'll never get either of them to acknowledge their crap - I think you know this - so just detach, detach, detach from them. 

Hi! Your post really resonated with me. It is so hard to set boundaries with mothers who are at one moment loving and friendly and the next moment cannot control their own feelings/anxiety/rage or separate out their own issues from their relationship with you!  It is nearly impossible to have a healthy relationship with someone who can't separate their "stuff" from their relationship with you. I really empathize with you - I recently got a voicemail from my mom where she gave me a list of things she was "sooo sorry" for (none of which ever bothered me or I ever complained about, and ignoring a lot of the things I have been very clear upset me and make me put distance between us for the sake of myself and my family).  Over and over, I come back to remembering that often the most compassionate thing for me to do is to have the courage to set boundaries, say no, and be clear about why I'm setting boundaries and saying no (even though I often feel guilty, want to give in, or convince myself that things have changed in the hopes that our relationship might be closer or easier). This last winter was the first time I didn't "give in" to spending time with her, and it was so healthy/lovely for us to spend holidays away from her! I know that until she can work through some of these issues, I need to proceed with caution and be very clear about what I will and will not tolerate.  I keep reminding myself that internally, I can accept her exactly the way she is (even if I don't need to put myself in the line of fire), rather than expect her to change - and regardless of how she reacts/what she does, I can behave the best way I know how and make decisions that feel good and in line with my own integrity.  My mom has made baby steps in the right direction, which makes it harder when she "reverts back" to old patterns. Every time, I feel duped! As for your sister, I'm not sure. My sister is in a similar situation and I'm not sure what to do about it.  I think everyone is on their own "path" - you can only control yourself and role model for her and support her. It's so so so hard!! For me, going to therapy was really helpful and allowed me to see my role in these patterns (I know I'm not innocent and have at the very least "allowed" her to be this way with me for a long time!).  Best of luck to you - you're not alone!! - Danielle