On Friday afternoon my SiL, her Dh (my brother), their toddler Ds, my sister and I went to my mother's house.
SiL can be a bit Pfb but I don't think that's relevant in the following instance. Over the course of the afternoon Sil was quite literally hovering over her son whenever he took a step anywhere. Dm told her to relax a little. Admittedly Dm's house isn't very toddler-proof but there wasn't an immediate concern about his safety at the time as he was just playing with some brick-type toys.
I decided to start preparing dinner so then my sister and brother went out to get somemore supplies. Although I can't be sure of their exact exchange, Dm told Sil to come and keep me company in the kitchen.
Sil comes along and we're enjoying a glass of wine in the kitchen and a while later we hear my nephew screaming and crying. We rush to the living room to see him covered in shelves and drawers. At some point he pulled a bookcase which isn't joined up on himself.
He wasn't visibly hurt but I'm sure it must've been a fright and quite painful.
At this point my siblings return and Sil demands that they leave immediately which my brother does complicity.
I know that my Dm and Sil have always had a bit of a difficult relationship but I'm sure she'll use this as an excuse to veto any future visits. Dm thinks that accidents happen and thinks Sil unreasonable for insisting to leave immediatly. My brother has only expressed concern for Ds so is sort of staying out of the family politics of it all and my sister thinks that Sil is going to be vindictive over this (a vindictive bitch - to use her exact words) and should get a grip.
I have a good relationship with all of them but I can see all points of view. Sil refuses to talk about it bar saying that she won't put her child at risk again in the future.