An Adelaide mother who laughed as she filmed her injured four-year-old daughter repeatedly falling off a motorbike has been jailed for at least four years for the girl's manslaughter. The Supreme Court of Australia has released chilling home video of a four-year-old girl who died at the hands of her mother and her ex-partner.The mother and her then partner made the 17kg girl get back on the 50kg motorbike over a three-day period, despite her suffering massive injuries from repeatedly falling off and crashing.When Chloe Valentine was eventually unconscious in a semi-vegetative state, Ashlee Polkinghorne and Benjamin McPartland waited eight-and-a-half hours before calling an ambulance.In jailing the pair in the South Australian Supreme Court on Wednesday, Justice Trish Kelly said putting Chloe on the bike in the first place was negligent as was failing to seek immediate medical help."You were prepared to let your child die rather than exercise any proper parental responsibility for her welfare," she told Polkinghorne, who was 15 when Chloe was born.Now 22, she and McPartland, 28, pleaded guilty to the criminal neglect manslaughter of Chloe, who was forced to ride the motorbike in the backyard of their Adelaide home in January 2012.Over three days, she suffered massive injuries after the bike repeatedly crashed into a shed and pot plants, fell on top of her and eventually smashed into a lemon tree.Polkinghorne was jailed for eight years and McPartland for seven, with non-parole periods of four years nine months and four years two months respectively.The judge said after Chloe became unconscious, the couple went on Facebook, accessed internet banking, googled what to do with an unconscious person and smoked cannabis.Polkinghorne had filmed her daughter on the bike, which was far too big for her, and McPartland was seen almost throwing Chloe back on after she fell off on multiple occasions.The judge referred to Polkinghorne's "evident amusement", referring to laughter heard on the video.Another video of Chloe opening her Christmas presents clearly showed she was extremely fearful of McPartland, Justice Kelly said.Polkinghorne, who has a borderline personality disorder, was described as manipulative and narcissistic.Unless she undertook psychotherapy, "any child you are responsible for in the future will remain at risk", the judge said.Chloe's supporters, who wore yellow ribbons, clapped and cheered loudly as the pair was jailed."Now you know how Chloe felt," called out one man as the couple was led from the dock.