My Mil is like this too, I realised she is a narcissist down to a T. And the more I read up about this the more I realise she’s an emotionally immature toxic mom. Unfortunately these people don’t change as they have a habit of making it all about themselves and hate it when boundaries are set but all you can do is try and keep your distance to protect your own mental health. Sorry you are dealing with this, it really is emotionally exhausting.
Unfortunately your DL was raised in that kind of household so he was used to it, couldn’t see what the problem is. My husband is the same, although he will admit his parents are weird, he is ok with it and doesnt want to set boundaries with them. I recommend to go counseling with your DL so hopefully he has more understanding how she is impacting you and your relationship with DL. So sorry to be in this situation. It is a tough situation.
Why are MILs like this?? I’m so sorry.