OP,
My dh has a saying. "Don't look for logic where it does not exist."
You're holding your sil to a standard that isn't in her realm.
I have read much of this thread and your sil seems immature and babied. My bil was treated like your dh's parents treat your sil bc of his personal problems. Personally, I think he is a selfish man but as a mother, I also understand trying to help the child who needs help/is deficient in some way.
I don't think she's as awful as you think. The picture thing is a problem bc it's financially stupid/scam.
There seems to be a power struggle. She's insecure/immature and you're unforgiving and want her to be different. She's not. She's herself. She's not introspective. But you can be different.
We found peace in our marriage with family when we compromised. He makes decisions for his family and me for mine. We each understand our own family dynamics.
Frankly, she seems lonely and left out. No dp. No dc. She seems to need attention.
Ignore the pictures bc it's a scam. But cut her some slack. You've got a better life and she's got mh issues. Be bigger and that will make your dh happier too.
