Cheryl Jones, 49, heard about the harrowing messages on her 30-year-old daughter' Karla James's wall and immediately rang Karla's mobile to find out what was going on – only for her call to be answered by a police officer.
She was apparently told: "Sorry but an officer will be around to see you shortly."
Cheryl said: "What makes me so angry is the appalling way I was treated by the police. I will never get over losing my beautiful daughter or the way I found out about her death.
"Complete strangers could see she was dead by looking at Facebook. But I only lived down the road and I didn't know."
Karla lived in a flat in Tredegar, South Wales, less than a mile away from her mum.
Cheryl has now made a formal complaint about the delay.
Her daughter Karla was pronounced dead at 8.17pm on July 23 but officers did not arrive until 11.38pm to tell her mother in person.
The mum-of-three was at home when her nephew Barry Llewellyn, 37, called to say he had read on Facebook that Karla had died.
Cheryl said: "My daughter was found dead and I only found out through Facebook.
"I was Karla's mother, her next of kin, the police should have come to see me straightaway."
She added: "I was hysterical. I had only talked to her hours before about her dog Scooby.
"She said she loved me before she put the phone down - she always did.
"She was the most beautiful girl inside and out and had a childlike innocence. She was a real chatterbox and loved people."
An inquest has been opened and adjourned while toxicology tests are carried out to discover what killed mother-of-one Karla, an aspiring model when she was in her teens, who suffered from heart problems as a girl.
A spokesman for Gwent Police said: "Inquiries were made to identify addresses for the next of kin to give the sad news of Karla's death but it was not discovered until 11.30pm.
"It is a sad indictment of today's society that an unknown individual made the decision to broadcast such tragic news without consideration for the family."
More on Parentdish: Does Facebook make new mums feel more vulnerable?
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