The MTV reality star, who died on Friday at age 34 after a long battle with cancer, was memorialized at the Church of St. Francis Xavier in downtown Manhattan.
The service commenced with the devotional song "On Eagles' Wings," with Brown's tearful family members following the casket to the front of the church.
"She is clothed with strength and dignity, and she laughs without fear of the future," read a quote from Proverbs 31:25 on the back of the program.
Yearwood sang "I Remember You," a song from her new album Prizefighter, that honors her late mom Gwen, who died from breast cancer in 2011.
Brown's sister Megan, 30, delivered an emotional eulogy, noting that before she prepared her remarks she revisited some of Brown's favorite spots, including Central Park and teatime at The Plaza Hotel.
"Diem loved hard, lived hard and danced hard," Megan told the attendees, at times choking back tears. "My mom always said that Diem came out fighting since day one."
On a lighter note, she shared a story about her and her sister selling Girl Scout cookies as children. They filled out an order form using names from the phone book, which scored them the "Kaboodle" prize they wanted – though when 900 boxes of cookies arrived, they weren't sure what to do.
Close friends Julie Rotondi, Erin Robbins and Alicia Quarles were among those who read poems and Bible passages.
"Diem was the happiest person I know," says Quarles, whose husband, Mike Ross, served as a pallbearer at the funeral. "Till her last breath, she never gave up. I can't even explain to you her divinity."
During a conversation two weeks ago, "She talked about her faith in God, her love of family," says Quarles, an E! News correspondent who invited her friend Yearwood to perform at the service.
Along with tears there was also laughter, with Quarles at one point beginning her reading too soon. "Diem is laughing at me right now," she said, as guests laughed. "We all know Diem forgives everyone, so she forgives me for that!"
Another friend read a poem, "The Impatient Patient," which was how the determined Brown often described herself. Friend and cancer activist Ethan Zohn, whom Brown had worked with via Stand Up to Cancer, read a letter from SU2C adviser Katie Couric.
"Diem's dream was to be a journalist," says Quarles, who also received support after Brown's death from SU2C co-founder Kathleen Lobb. "Katie's letter hit on the point that cancer did not take away her dream. A journalist is a truth-teller who informs people. Diem did just that by reporting on and letting the world know what it is really like to battle cancer."
The service concluded with a musical slideshow of Brown through the years, from her childhood in Georgia to her sorority days at Florida State University to her reality TV career, which elicited tears from the guests.
In the program, Brown was remembered by her given name, Danielle, along with her late mother Jillian, who died in 1999.
"Our dancing angel, Danielle Michelle Brown, is watching from Heaven's window with her mother, Jillian Catherine Brown."
Editor's note: While there have been numerous conflicting reports about Diem Brown's age, PEOPLE has been able to confirm, via public records and with family and friends, that she was born in 1980 and was 34 years old at the time of her death.