The Crown is trying to prove that the three were racing each other to a family cemetery, leading to the accident.
Ms Allan said she pulled a passenger from the front seat of the car Reihana was driving as he paced up and down the road.
"The driver was saying, 'Aunty made me do it, I knew I shouldn't have driven, I've had too much to drink."'
Ms Allan said the situation became more volatile as family members from a nearby house arrived and began arguing.
"The behaviour of the people there was quite distressing in that there was more concern about who shouldn't have been driving than finding the people in the accident, for example the body [of Merepeka] that lay there on its own."
In a recorded interview shown to the jury, Davey told police that he, Morehu and Reihana were all "medium drunk" when they drove off from Morehu's home.
Another witness, Brent Rogers, recalled hearing a "sonic boom" just as he and several of his friends were about to tuck into their Christmas dinner.
Mr Rogers ran to the scene and found a delirious Reihana moaning and crying.
St John Ambulance paramedic Leanne Barnett said she examined Reihana, who confirmed he had drunk "a couple of beers" and about five shots of vodka.
"He said he didn't want to drive ... at one stage he said his aunt [Morehu] put the keys in his hands."
The trial before Justice Murray Gilbert continues.