How can I help Her???

My best friend's lil sister lost her boyfriend tragically sunday night. He was on his way to drop her off at her house when he got a call from his friend needing a ride. They went to a meeting place to meet some body that owed him $$. She saw that his friend had a gun and a bat not knowing he was goin to rob them instead. She saw a truck pull up and hid in the back seat, then heard gun shots from outside into the drivers side,then thru the pengers side. When the truck drove off she tried 2 push the seat where she saw nothin but parts of his skull, she then tried to get help. Her b/f and his friend died instantly had no chance. She witnessed all this and yet she cant understand y. He was known to help others before himself and never had enemys, he was just @ the wrong place @ the wrong time. How can we help this young tramatized girl deal with the loss of her love and actually living the nightmare over and over. I dont think there r any words for her to begin to heal.