I don't post very often but this is something I really need help with please.
My younger brother (FRANK) recently got married to a lovely girl (SALLY) that our family adores. The issue I have is that my mother (MOM) frequently says very mean things about my brother to her in front of groups of people, family, strangers, my brother, it doesn't matter who is around. Everyone must hear her opinion.
Example when someone meets Sally for the first time:
Mom- Have you met Sally? She's so great I love her so much! Sally you know you married beneath you right?
yup, apparently my brother Frank is not good enough for Sally.
It's not just that, Mom brings this up ALL THE TIME. She has said to my brother Frank "You are lucky to have Sally, she can do so much better than you!" I can give other examples but its all the same message. Sally is awesome, Frank is not.
Perspective- My mom says this is a somewhat teasing way (even friendly) but she seriously believes what she's saying. That Sally is too good for Frank and she can do so much better. Family and friends have called her on it (

why would you say that about your child?!???) she just laughs it off and says its true.
So here's some background on my family that I think is relevant - Frank is a miracle baby. He was born with serious health problems and is the only known child to recover. He has some lingering health problems, lung issues, ADD, ADHD but nothing serious. He will never run track but that's pretty much the extent of his "disability" all in all, he's healthy and a really good kid.
Let's compare Frank to me. I'm a drug addict and started using at age 12 (Sorry NA says I am a RECOVERING addict, whatever). I dropped out of school, I sold everything of value I could from Mom and Frank to feed my addiction. I was a very bad person. I've been clean for a couple years but what I have done in the past still fills me with deep shame. I've hurt all of my loveones and came close to ending up in jail for life. My addiction and actions are not a secret in my family. Everyone knows I was the one who messed up and my family uses me as an example of what not to do with your life. I encourage this. The last 20 years of my life are the best PSA you can give.
Anywho, I'm not married. I'm somewhat financially stable and in no way mentally stable. I am not what anyone wants to go up to be.
Despite all of that, Mom always says how much better I am than Frank. To everyone!

I am so proud of Frank because he made good of his life. When I was was his age I was not nearly as well off as he is (mentally, financially etc). This is also not a secret in my family. In fact my father frequently echo's my sentiments, that he's glad Frank did so much better than he did.
So here's the etiquette- I need a phrase or something to stop my mom to say these horrible things about Frank. Both he and Sally (and other family members) have come to me voicing their discomfort with my moms statements. It breaks my heart because Frank keeps asking me what he did wrong and why mom would think this way about him? Sally is so uncomfortable around Mom, we all are.
To make things even worse, Mom *truly* does not understand why what she is saying is wrong, she *truly* believes Sally is too good for Frank.
Cut direct is not an option. To do that would destroy her more than her hurtful words hurt us.
"Mom, what you said was really hurtful!"
"So? It's true!! LOL!
What can I say after that?
