I don't know if all small communities do this; probably not big cities, but it is the custom here to pull to the side of the road for any funeral procession, either direction. Even if you are on a 4-lane road, if you see a funeral procession, you pull over out of respect for the deceased and family. In the past, I have at times felt impatience with this custom. When you are in a hurry, it sometimes is "inconvenient" to have to pull over and wait for what seems like a long time. But when my Dad died, as we were heading to the cemetery for the burial, my son said "You know, I never could see the sense in everyone pulling over for a funeral. It's not like you know the person, or anything. But now, I understand why it is done, and how much it means to the family, because it really affects me. It is showing you respect them in their mourning." From that day on, I have looked at the custom with new compassion, and I am so glad we still do it around here.
I can't imagine how that poor family is coping. My heart aches for them. But I do think it is good for your daughter to have gone and participated, and have seen her friends there crying. We all have to learn that mourning is one of the human feelings that are real and necessary, and that we do get through it eventually, but it changes us.