Ian Glover has been jailed for five years after he crashed into teaching assistant Laura Jane Thomas's parked car on the A5 between Telford and Shrewsbury in Shropshire last July.
Thomas, 20, and her fiance Lewis Pagett, 19, had broken down and pulled on to a grass verge with their hazard lights on. When Glover's 44-ton Mercedes truck hit their car, it flew over the barrier, killing Miss Thomas while her fiance was speaking to his father on the phone.
Thomas was a teaching assistant at Marshlands Special School and volunteered with the Riding for the Disabled Association. She was planning to marry Mr Pagett at the same venue her school prom was staged.
Glover, who had worked as a driver for Sainsbury's for ten years, admitted causing death by dangerous driving and causing serious injury by dangerous driving.
He told police that he could not remember what had happened before the crash, but tests on three mobile phones found in the lorry revealed that he was looking at explicit sites while driving.
Miss Thomas's mother said: "A five-year sentence for killing our beautiful daughter is just not enough in our eyes. What is worse is he could get a shorter sentence if he's well behaved. Laura had lived just a quarter of her life and he could be out of prison in two years or so – it's just not fair."
Mr Pagett, who was left with a head injury and fractured vertebrae, said: "Laura and I were looking forward to planning our wedding together – instead, I ended up planning her funeral."