My Mum did this!
She stopped talking to my DB and his girlfriend over exactly the same thing (long history there and she is MIL to my DB's girlfriend IMO).
Because they came up to visit and were the first to out of my family my mum got the ar*e and blanked them for 3 days. The reason being is that she doesnt drive (she's only 9 miles away), and they should have asked her if she wanted to come (even though she was at work - they work shifts in the police and paramedics btw).
I didnt see my mum n dad for 3 days after my DS was born (my 2nd) because they were so busy with work blah blah blah. But she got the hump with the ones that did come and see me. Nice.
Do feel for you oops. Families are hard work even at the best of times.