Rachel Bradford relived the trauma of watching her six-year-old daughter Coco die in July 2017 after being treated initially in the Royal Cornwall Hospital at Treliske, Truro.
She broke down several times as she read her statement at an inquest into her daughter's death, which started today (November 29).
Mrs Bradford said: "We were treated with utmost contempt by healthcare professionals from Tresliske Hospital, I use the term professional loosely."
She told the senior Cornwall coroner Andrew Cox a series of failures contributed to her daughter's death.
She said: "There were multiple opportunities to change the course of her treatment which would have saved her life."
She wept as she told her Coco - who was autistic - died in front of her eyes and there was nothing she could do to save her.
"She was my absolute world. I have cried every day since."
The inquest heard Coco had been "happy and healthy" and "resilient and strong" before she began being sick and suffering with diarrhoea in July 2017.
She was admitted to the Royal Cornwall Hospital at Treliske in Truro but was sent home until the next day when she was admitted to a paediatric ward before going into intensive care.
She was later transferred to the Bristol Children's Hospital where she died on July 31, 2017, from multi organ failure and E Coli 157.
Mrs Bradford said while in the Cornish hospital she believed staff thought she was "overreacting" and being "over-protective" as her daughter's temperature reached 39.2.
She said: "We were concerned. No one seemed to know what was wrong with Coco."
She accused one doctor of being "dismissive, rude and arrogant" and said there was "an air of nonchalance".
She described her husband Luke getting angry with staff and said: "We were concerned about sepsis. Coco had developed sepsis by this point.
"Coco was in so much pain, it was glaringly obvious."
She added she was terrified Coco would die and she tried to get that thought out of her head.
Mrs Bradford said medics claimed Coco was "non-compliant and uncooperative" and dismissed that saying: "She was neither. They upset her and were hurting her. She was dying in front of our eyes."
Mrs Bradford told the hearing in Truro "there were failings in the most basic level of care" and many things were not acted upon and they did not accept human error should be a factor.
She accused staff of telling lies even when evidence in clinical notes contradicted this adding all their concerns about C Diff, E Coli and sepsis were dismissed.
Mrs Bradford said Coco's death had left her family "fractured" and she ended her statement by saying: "We just want the truth... but suspect that will never happen."
A highly critical independent report after Coco's death concluded she died after medical staff missed several chances to save her life.
The Royal Cornwall Hospital NHS Trust accepted there were a series of failures and apologised unreservedly.
Coco was not treated for dehydration and there was a delay in giving her antibiotics when symptoms suggested she had sepsis.
The inquest is expected to last two weeks and will hear evidence from a number of doctors.
The hearing continues.