How far should you go to keep extended family together ?

I am involved with a woman who really is going thru a hard time, not for anything she has done. She is a sweetheart. The problem is that her niece, not too long ago, tried to set up arrangements for her grandparents who are getting elderly and probably should be involved with ited living. At the time, the parents were staying, reluctantly with the parents of the niece, who took on the position of trying to get all of the siblings and cousins together for a family meeting, to see how everyone could do their share to help. All good intentions, but some of the cousins (my gals children) hesitated to have this meeting, due to past dealings with this niece. The consensus from my gals side of the family was that my gal and her sister would decide the best approach to this situation with their parents. With this, the niece has been quite upset, missed family showers, weddings, just ignored the extended family. Whe one of her cousins tried to open the door to compromise, she was blasted out of the water....and this was three months after the initial problem. Now I am pretty new into this family, they are good people...lots of ego stuff, as in any family. But I have found that putting these situation out into the "Answers" world has always helped me.....so pleeeeze if u can help these nice people get past this pretty high speedbump....I feel in time, it will sadden the grandparents, with Thanksgiving, and Christmas coming up....and they are in their mid 80's...At this point, all they want is peace!...They are adorable...just slowing down.