The daughter of Lord Young has died at the age of 25 after she complained of a headache while on a bike ride.
Gaia Young was taken to hospital after falling ill during a bike ride with friends on July 17.
Doctors said that she seemed "confused" and was falling asleep when she was at University College Hospital.
Gaia suffered from a "sudden, severe headache with awful vomiting," according to her mother.
An inquest held at St Pancras Coroner's Court showed that doctors first suspected Gaia of being intoxicated but she did not drink excessively or take recreational drugs.
They also suspected heatstroke and dehydration, but there was no underlying cause found for the healthy woman's symptoms.
Gaia's mother Dorit Uhlemann, Lady Young, now believes that her daughter did not receive the proper care and that there was a chance to save her.
Lady Young said: "I believe that with proper care she need not have died. I believe she lost the chance to live.
"How can it be that a previously healthy young woman dies in a hospital and yet nobody knows why."
Lady Young told the inquest that she was "not kept informed" on her daughter's care and that medics "completely misdiagnosed" and "misread" signs of her illness.
"[Gaia] was a responsible, polite, clean-living young woman with a keen interest in her own health and in her intellectual and professional development," she said.
Lady Young was adamant that Gaia was not intoxicated, but Dr Zoe Veary said that this was considered "because of her age and her history of being with friends."
Additionally, Dr Veary explained that Gaia appeared very "dehydrated and agitated" and was rolling on the bed while clutching her stomach.
Gaia was given fluids at the hospital but her condition worsened quickly and she eventually stopped breathing on July 18.
Doctors were attempting to conduct a lumbar puncture when Gaia experienced respiratory arrest at around 3pm that day.
They said that after she stopped breathing, there was no "neurological recovery" and Gaia later died on July 21.
Doctors now believe that Gaia had cerebral edema, a condition which causes the brain to swell due to fluid developing in the brain.
But, medics are still unaware of what caused the cerebral edema in the first place.
Dr Thomas Samuels, who was involved in conducting the lumbar puncture, said that "communication during the course of the day would ideally have been better" with Lady Young.
But, he maintained that doctors at UCH made the right medical decisions in response to Gaia's symptoms, adding: "I wouldn't have done anything differently."
Dr Christian Hasford, who visited Gaia before the procedure, explained that she could have developed a cerebral edema due to toxins or inflammation.
He confirmed that it was unlikely to have been caused by "alcohol or a conventional recreational drug."
The inquest will continue this week, as no clear medical cause of death has been found for Gaia's death.
Gaia is the daughter of the social entrepreneur and Labour peer Michael Young.
Her mother paid tribute to her "much-loved, beautiful, and healthy" daughter in a written statement.
