You've probably read about my ongoing issues with my mil on other threads.
Basically dh went nc with his dsis after she ignored our dd from birth- she was apparently mad that he didn't have enough time for his nieces and other slights she'd wrongly took Offence at- we tried number our times to sort things out she wasn't interested- just increasingly nasty and vile (FB rants, abusive msg etc).
Mil blamed us entirely for the fall out in the beginning and went on to try to ruin our wedding beforehand and during because we hadn't invited the dsis.
Since then mil said she had spoken to a few friends family members and realises that dsis actually was the root of the arguments and she was going to remind neutral from then on she wouldn't be picking sides anymore.
It was her 60th bday last weekend she told dh she wasn't going to have a party- you know what's coming next...yes there was a party the dsis and her kids were invited obviously we were not and our dd was excluded yet again (we've been told mil can't see dd at Xmas or last Xmas because it upsets the dsis too much!)
I'm just mad my dd is treated like a second grade grandchild because sil stamps her feet its ridiculous.