If DD and SiL have been "pandering to her" all her life, there's no point you trying to say anything against it now.
On various threads, on GN, people have said that something generally considered ungrammatical is actually part of normal speech in their area.
Don't allow your DGD's mood to dictate how you feel. It is disconcerting if she behaves illogically but it's best just to let it flow past you.
As others have said, your recent loss may be affecting your own moods and reactions. Please try to keep harmony with your family. 
Doctors and how they come across
keep away from all pubs this coming wednesday


