Ouch! Good job poor little George is too young to understand that. She's obviously hurting but I hope they don't go too far into melodrama with Mary's storyline - I'm more interested in seeing how she recovers than watching her mope about wearing black all series.
Although, I think Mary *IS* right to hate the baby; if it wasn't for George coming early, then Matthew would not have been driving home that day and would not have hit the tree in an attempt to avoid the truck.
I think she blames George - for being born a month early - for causing his father's death, thus the reason she dislikes him.