Read post 795 and 797 this thread .
SW asked her MIL to not have nuts in the house when they visited, in July. She replied that she never bought them. MIL was aware that Celeste had a deadly allergy to nuts, and the presence of them could have caused anaphylaxis . So, when they get to the house lo and behold there is a large bag of pistachios, out on a counter in the kitchen.
SW gets perturbed at this,tells MIL and the bag of nuts is put away. The following day, MIL gives an ice cream with NUTS on it, to another child in front of Celeste. When SW reproaches her about this MIL says " she has to learn that there are some things she can't have". SW is then upset, takes the girls and leaves and doesn't plan to ever go back. She calls CW to tell him and in turn he calls his mother to complain.
There was VI on this forum who said she was present when this happened and implied SW was over reacting. She said the pistachios were unopened, were out of reach and blah blah, not worried that they could have caused life threatening reaction just by being in the same room. As Gitana said, this comment came from someone who clearly loathed SW.