Did Sophia actually witness Omar die?
Also, there is a mod over at Mod the Sims that takes away autonomous mourning. I am not sure if it is tied to traits, whether or not those who witness grieve more (that is my standing theory) or if it is just programmed that way.
I have a sim who is a lot like Sophia. She witnessed her father die and would not stop mourning and soon took up drinking. She was also a highly skilled gardener.
On the other hand, a sim completely non-related to but living in the same house as the father, also would not stop mourning. I had to install the mod because I play a Legacy and keep all tombstones on the lot and on the familial graveyard. It has helped a lot and the ghosts/sims/family are all happy. Plus I can have them mourn when I want to.
EDIT?: Holy cow your forum avatar is precious.