"It's a tragic loss and I'm hoping this is a wake-up call for all the young ones. When they just make a split second decision ... look what it does to all the families," Mrs Brown, whose granddaughter Riyani Lowen, 16, died in the accident, said.

"You see other families over the past few months in the same situation and think it will never happen to us, we'll be right. But it's not that way."

Mrs Brown and husband Max travelled from Healesville to comfort daughter Emma Lowen, who gave birth to Riyani when she was 19. "They had sort of grown up together. They were very good friends."

Also mourning are Riyani's father John and 13-year-old sister Casey.

Mrs Brown said the family was trying to keep going before the funeral was held, as "when it comes we're all going to go into a screaming heap."

Mrs Lowen, who lives in Narre Warren South near the accident site, has been too distressed to go outside.

"But she will have to pass the accident scene at some stage. It's going to be very hard."

Mrs Brown remembers Riyani as a "very sensible girl" with ambitions to work in the sports health field.

"We don't know what went through her mind [when she got into the car as a passenger]," she said. "Teenagers make very quick decisions."