The mother of Lyra McKee, the Northern Ireland journalist shot dead by dissident republicans, has died weeks before the first anniversary of the murder.

Joan Lawrie died in hospital in Belfast on Tuesday night, her daughter, Nichola McKee Corner, said in social media posts.

“Passed away last night of a broken heart. Unable to live without her baby Lyra,” she tweeted. “Hold Lyra in your arms reunited once more, and send us strength.”

Lawrie’s health deteriorated after the death of McKee, 29, her youngest child.

A New IRA gunman shot the journalist as she observed a riot in the Creggan neighbourhood of Derry on 18 April. He was aiming at police Land Rovers, behind which a crowd of residents had gathered. The group later apologised.

The killing shocked Northern Ireland and piled pressure on politicians to revive the region’s moribund assembly and executive at Stormont. It was restored in January after the general election.

McKee had moved to Derry to live with her girlfriend, Sara Canning, and used to return to north Belfast to look after her mother, who had a disability.

The tragedy thrust Lawrie into the spotlight. She collected posthumous journalism and writing awards for her child. She wept last August at the launch of Angels with Blue Faces, a book Lyra had written about the 1981 Provisional IRA murder of Robert Bradford, an Ulster Unionist MP.

Lyra had paid tribute to her mother in an essay, Letter to my 14-year-old Self, that recounted her disclosure that she was gay.

“You will be sobbing and shaking and she will be frightened because she doesn’t know what’s wrong … you have to tell her because you’ve met someone you like and you can’t live with the guilt any more. You can’t get the words out so she says it: ‘Are you gay?’ And you will say, ‘Yes Mummy, I’m so sorry.’ And instead of getting mad, she will reply, ‘Thank God you’re not pregnant’.”

McKee, an LGBT activist, was cited last year when same-sex marriage was extended to Northern Ireland. Murals of her have appeared in Derry and Belfast. Faber & Faber is due to publish an anthology of her work, titled Lost, Found, Remembered.

Prosecutors have charged Paul McIntyre, 52, with murdering McKee, possessing a firearm and being a member of the IRA. He denies the allegations.