I gather it's either a SIL of DIL from your post, I think it would be best to be the bigger person not for you but for the sake of an DGC involved. Do you want a rift for that child to witness.
It will be hard and you may never find out what or if you have ever done anything wrong, sometimes even a tone of word or look on someone's face can upset someone.
It happened in a similar way with our DIL (she never sent a letter) but stopped speaking or visiting for 9 months. We asked our DS if or what we had done wrong even he didn't know. So we both ignored this, DS brought the DGC'n to visit or spoke to them on the phone. Then all of a sudden she came to our home as though nothing had happened. Back to normal but I will keep this slight in the back of my mind.
How do you acknowledge Easter.
Is anyone interested in the terror attack in Moscow?
Exploratory Essay Help: Navigating the Uncharted Territory of Writing