Why would a grandparent show favoritism towards some of her grandchildren and not others?

Please do not respond unless you read the details.

My husband had a falling out with his younger sister in February. She said very hurtful things about Jon and I and she disowned us. She has two adult daughters and a 16 year old daughter. My husband’s mother lives with his sister, about 90 miles from where we live.

Since the falling out I’ve noticed that grandma doesn’t respond to any accomplishments that I post on fb about my daughter, yet grandma is all over posts about her other granddaughters telling them how much she loves them. She’ll even post about these girls, but never my daughter. Grandma also didn’t acknowledge our sons for their birthdays this summer.

I don’t think this is affecting our daughter. Grandma has always been kind of flakey, but this year has been different since the fallout. My husband won’t talk about it, so I’m left observing and wondering.

My children have my father who is wonderful and they had my mother who was equally awesome. My parents may have had issues with their children but they always let us know they loved us and they never ignored their grandchildren. I just can’t understand doing this to your own grandchildren.

What the heck do I do?