Pippa McManus, 15, weighed about 4st (25kg) when she was being treated at The Priory in Altrincham.
She was released in December 2015 and later died after stepping in front of a train near Stockport.
A lack of support available to her family contributed to her death, Stockport Coroner's Court heard.
The jury returned a conclusion of suicide but found the care plan when Ms McManus was discharged was inadequate and there was not enough communication with the family about her suicide risk.
Inadequate community care and specialist support and a lack of cohesiveness amongst agencies were also contributory factors to her death, the court heard.
Speaking after the conclusion, her mother Marie said there should have been more help available and "too many of our children are dying from this terrible illness".
"Effective treatment is needed more quickly and if this had been available to our beautiful daughter, maybe she would still be alive today, maybe we would not have needed this inquest," she said.
Paula Stanford, hospital director at The Priory, said: "Our heartfelt sympathies are with Pip's family and we will now carefully consider the findings of the jury."
During the inquest, the hospital said her anorexia was one of the most severe cases it had seen.
The coroner, Andrew Bridgman, said he will write to all of the agencies involved in her care.
The inquest heard Ms McManus had a history of self-harming and had previously written a number of goodbye notes to her family, doctor, and The Priory hospital.
By the age of 13, she had been diagnosed with severe anorexia and was obsessed with diet and exercise and in September 2014, was sectioned and treated at The Priory.
She was released in December 2015, by which time she was not considered high risk, though she remained under hospital care.
But following a family row five days later, the teenager walked to Gatley train station near her home and killed herself.
Her father, Jim, said his daughter's anorexia "had too strong of a grip."
"She used to say she had bad thoughts and wasn't allowed to do things - she couldn't even lick an ice-cream. She'd turn around and say I'm not allowed.
"Whatever was going on in her head was so strong she just couldn't comply."
Her mother, Marie, said it "was just horrific" and "a nightmare."
"[Pippa] hated herself. She thought she was the ugliest person in the world. Whatever you said, it didn't make a difference because that's what the anorexia was telling her.
"We needed some trained mental health workers to work with us but they weren't there to do that... We were let down by everybody I think. Everybody had a part to play."
Deborah Coles, director of INQUEST, a charity that supported the family during the court process, said her parents' "concerns were dismissed and minimised throughout".
"Pip's death has exposed a mental health system which pushed through the discharge of a highly vulnerable child without any of the support or care in place to make sure she would be safe," she said.
No adequate care plan was in place for an anorexic teenager who killed herself five days after being released from a psychiatric hospital, an inquest found.