Chrystal Ross died following a suicide attempt at the Mount Barker Hospital after being told she was going to be discharged.
The 24-year-old was admitted in January 2015 to help manage her anxiety and depression.
After 11 days in hospital, Miss Ross, who was under the impression she would be transferred to Glenside Hospital, was informed she would instead be discharged.
The following day she was found unconscious in her room after trying to take her own life.
Staff managed to resuscitate the patient before transferring her to the Royal Adelaide Hospital, but after three days on life support Miss Ross was deemed brain dead and died.
A coronial inquest into her death started on Monday, and Miss Ross's mother, Michelle van Dyk, spoke as a witness at the hearing.
"Her beautiful life was cut so tragically short and we are here today to ensure that this doesn't happen to someone else's loved one," she said.
"Somehow, someway, something went horribly wrong and I want to ensure that we are able to find out the truth about what happened."
Michelle van Dyk described her eldest daughter as a beautiful young woman who was living a full and happy life. She was engaged and had built a house with her partner.
In January 2011 Miss Ross suffered an injury at work and was placed on WorkCover.
As a result of chronic pain and the loss of ability to do simple tasks including her passion for drawing, Miss Ross's mental health spiralled.
"She became closed off and became almost zombie-like," Ms van Dyk said.
The council assisting the coroner, Kathryn Waite, told the court today that Chrystal Ross had been told she was going to be discharged the day before she took her own life.
"If she had been transferred her death might have been preventable," Ms Waite said.
She also said Miss Ross received mixed messages about her medical treatment.
Ms Waite said in her opening address that when Miss Ross was told about her discharge she said: "I'm scared, please don't send me home."
A registered mental health nurse had already requested a bed at Glenside Hospital for Miss Ross but the patient was put on the waiting list.
On January 19, 2015, the same day Miss Ross attempted to take her own life, the Adelaide Hills Mental Health Team received a notification that a bed was available at Glenside Hospital, but the bed was declined.
"It's not clear who was ultimately responsible for the decision-making around whether or not Chrystal should be transferred to a specialised mental health unit and indeed why it is when a bed became available it was turned down," Ms van Dyk's lawyer Dimitra Dubrow said.
The inquest will continue on Tuesday and is expected to run for five days.
