Hi Phoenix,
So glad you were able to get all that off your chest!
Something that struck me in what you wrote was about hating to have to let this all roll off your back. And I'm going to say something you might find strange - who said you had to let it all roll? Who said you weren't allowed to be hurt? Who said that you were supposed to take anyone's insults? Who said you had to suck it up?
Now, here's another way to look at it: someone has insulted you. Acknowledge it. Feel the hurt. Don't try to run from it, don't try to be the "bigger person" and pretend that you can take it. Don't fight off the anger and embarrassment you feel. Just let it happen. Cry if you need to, but just let the feelings happen.
What you will find if you just allow the feelings to happen is that a) it won't kill you and b) it passes. Quickly. I know it sounds counter-intuitive, but I promise it's true!
Putting our own feelings aside is NOT accepting a situation. This is often confused for acceptance, but actually it is denial of just how crappy something is making us feel and we don't want to feel it. Acceptance is acknowledging fully all the pieces of a situation, no matter how ugly. You might be thinking:
-My mom said I'm weak
-That hurt me to my core
-I doubt my strength now, am I weak? Is she right?
-I'm angry that I doubt myself
-Why doesn't she love me?
-My heart hurts that she hurts me so easily
-I hate feeling this way
-Now I'm complaining and I am embarrassed. How did I fall into this trap?
Is there anything wrong with thinking or feeling any of the above? Of course not. They are legitimate thoughts and feelings. The key is to accept them and then move on. Accept, not deny.
I thought I had put my wall back up. I thought I had shut her voice out and made so much progress on believing in my own value and not caring about what she thought. I've worked so hard on convincing myself that my M's opinion of me was not going to define me. I accepted that it meant something to me and admitted that I was disappointed by it but I would not let it get me down.
You've done a great job already! You've learned some great skills, learned your boundaries. Now learn how to be kinder to yourself!

Just because you've been hurt by this recent contact doesn't make you a failure! Someone has just slapped you in the face, so naturally it's going to sting. You wouldn't be human if it didn't. Where your skills come in, is in how you are able to acknowledge, accept and keep moving on after the slap happens.
Cheerio nails this for all of us with BPD moms:
If you were drunk in an alley somewhere she wouldn't complain about you more, and if you were queen of England she wouldn't complain about you less. The amount she tries to tear you down correlates with her level of emotional turmoil, not with your life. She's calling you weak because she feels out of control emotionally (perhaps she's the one feeling weak), and not because of anything about you. That's why there's no convincing her that she's wrong about you -- her criticism never had anything to do with you in the first place.
Wishing you well, you're doing a great job so far!