Sobia Yousef, 36, grabbed a knife from the shelf on the kitchenware aisle of the Shipley Asda store and cut her throat.
On the morning of her death Mrs Yousef sent her two surviving children to school before leaving the house to walk the 15 minutes to the supermarket.
She was pronounced dead at the scene by paramedics.
Mrs Yousef had been suffering from severe depression and psychotic episodes after her daughter, Meweesh Mahmood, was admitted to Leeds General Infirmary, with severe complications resulting from a congenital heart defect in July 2013.
Bradford Coroner’s Court, heard that when she had visited her daughter at Leeds General Infirmary, she had alarmed staff there by claiming she could see cats in the room, had frequently called out to God to save her daughter and believed that black magic had been used on Meweesh.
By the end of July Mrs Yousef had been sectioned under the Mental Health Act after she was diagnosed with severe depression with psychotic elements.
In a statement to the court, Mrs Yousef’s brother, Imitaz Ali, said his sister had made a number of strange and irrational decisions during the course of her illness.
He said: “My sister was doing things that were very unusual. She took all her jewellery and put it in a handkerchief, tied it together and threw it into a mosque letterbox.
“At the time the mosque was closed and so her aunties had to go find the man with the key to get it back.
“She also withdrew £2,000 from the bank, went to Western Union and sent it to Pakistan saying it was for ‘the poor people’.
“Sobia would stand out in the rain for hours and we were worried that she might hurt herself accidentally.”
Mr Ali said that after Meweesh’s death Mrs Yousef took all her daughter’s clothes out of the wardrobe, piled them on the cooker and turned the hobs on.
Her husband, Tariq Mahmood, who was sleeping upstairs at the time, smelt the smoke and came downstairs to find them on fire, before managing to fling the burning clothes out into the garden.
Mr Ali said while her daughter was still in hospital Mrs Yousef cut all the electric wires to the boiler in her home because Meweesh had told her that she was too hot in her hospital bed.
He added: “I spoke to doctors who said it wasn’t their problem because she had been discharged.
“One support worker who took her to the park said she was improving, but she was not improving. Everybody who lived in the street knew she was poorly. She would stand out on the street corner for hours on end.”
During her illness Mrs Yousef became distant from the family and would refuse to speak to them or see them.
The inquest continues.