Lyra McKee revealed plans to suggest her partner Sara for only a few hours before she was murdered, and the mourners heard at their funeral.
When Stephen Lusty spoke in St. Anne's Cathedral, she said she had shown him pictures of the engagement ring.
Ms. McKee was shot dead Thursday while watching rioting that evening.
Prime Minister Theresa May, Irish President Michael D. Higgins, Taoiseach (Irish Prime Minister) Leo Varadkar and other politicians are on duty.
The New IRA said its members killed them.
"She showed me pictures of the ring she had bought for Sara and told me about the fabulous plans she had made in May," Mr. Lusty said.
"She let me put a date in my diary at the wedding in Donegal in 2022 and gave me strict instructions to wear my sash, which she always lends, decorate with Harry Potter, and find or retrieve my own version of Sara .
"That was our Lyra ̵
"When we hugged each other and said goodbye, I saw both the sparkle of the girl's innocence that I had met all those years ago, and the radiant confidence of a young woman who blossoms to greatness."
DUP leader Arlene Foster sat next to the Sinn Féin leaders Michelle O'Neill and Mary Lou McDonald.
Also in the service is the pastor who witnessed the decommissioning of the IRA, Rev Harold Good.
- Their commitment to the truth was absolute.
- Timeline of Irish Dissident Activities
Many journalist friends wear t-shirts, scarves and badges from Harry Potter to the funeral service in St Anne's Cathedral. Ms. McKee was an avid fan of the series.
At the beginning of the service, Dean Stephen Forde said: "Lyra was a person who broke barriers and crossed boundaries, this was her trademark in life, this is her inheritance in death."
"As a journalist, she sought the truth wherever it went, she never contented herself with the grim silence of unanswered questions. "
She was a primary student in Nordbelfast when the agreement was signed.
" She grew up and championed for her hope A society that was free of the prejudices of the past. "
" Dark Days "
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P Joe Gormley, who anointed Mrs. McKee after her death The BBC News NI said there was still "a big shock" in Derry.
"But people also reflect and know that we are faced with a choice in life," he said.
"We either go back to the dark days or go on."
He said he was ready to "sit down" with those in charge.
Colleagues of the National Union of Journalists (NUJ) are to form an honor guard at the cathedral.
The union described Ms. McKee as "one of the most promising journalists" in Northern Ireland.
Ciarán Ó Maoláin, secretary of the Belfast Union, described her as "intelligent, determined and very funny".
Guildhall Square in Derry also had a gathering for those who could not attend their funeral.