"If you're not outraged, you're not paying attention," the quote, displayed on a purple background, reads.
"They tried to kill my child to shut her up. Well, guess what? You just magnified her," Susan Bro said to loud applause Wednesday at the city's roughly 1,000-seat Paramount Theater.
Virginia Gov. Terry McAuliffe and US Sen. Tim Kaine joined her relatives, friends and others for the late-morning public service in a city still coming to grips with Saturday's protest.
Heyer's friends have said she joined the counterprotesters to oppose racism and injustice. Her mother pointed to the Facebook message that Heyer posted in November.
"I want you to pay attention, find what's wrong ... and say to yourself, what can I do to make a difference?" Bro said. "And that's how you're going to make my child's death worthwhile.
"I'd rather have my child, but by golly, if I've got to give her up, we're going to make it count."
McAuliffe after the service called for healing, reconciliation, and further moves past bigotry and racism. "We need to come together as Heather's mother spoke about," he told reporters outside the theater. "To make her life impactful, we need to move forward."
'She wanted equality'
Heyer, a paralegal at the Charlottesville-based Miller Law Group, had told co-workers Friday that she was going to be among the counterprotesters rallying against the "Unite the Right" groups.
She was walking along or across a street when a Dodge Challenger slammed into pedestrians and another car. Heyer was killed, and 19 others were injured.
Police arrested James Alex Fields Jr., 20, of Ohio, that afternoon after they found the damaged Challenger. He is being held without bail and faces one count of second-degree murder, three counts of malicious wounding and one count of failure to stop in an accident that resulted in death.
At Wednesday's service, her father, Mark Heyer, choked up as he spoke of his daughter. "She wanted equality, and in this issue of the day of her passing, she wanted to put down hate," Heyer said. "And for my part, we just need to stop all this stuff and just forgive each other. I think that's what the Lord would want us to do."
The racial diversity of those in the auditorium, he said, reflected Heather's embrace of people of all colors.
"It didn't matter who you were or where you from," Mark Heyer said. "If she loved you, that was it -- you were stuck. For that, I'm truly proud of my daughter."
Many wore purple -- a color she loved.
"Purple is a symbol of openness -- It basically lets other people know, 'I'm willing to work with you.' That's something that Heather was," her supervisor Alfred Wilson told CNN's "New Day" before the gathering.
"She was a person that was willing to work with anyone," Wilson, wearing a suit and a purple bow tie, said. "She was a very kind, generous person, and someone that actually was very opinionated and spoke up for what she believed was right."
Friend: She was afraid protesters would be violent
Heyer was nervous about counterprotesting on Saturday, but felt she needed to be there to stand up what she believed in, her co-worker and friend Victoria Jackson told CNN a day before the service.
One of the last conversations they had before each left for the weekend was about the rally.
"Heather said, 'I want to go so badly but I don't want to get shot. I don't want to die,' " Jackson remembered.
Heyer was afraid of the protesters because she believed they were not here for peace, her co-worker said.
'Defending the rights of others'
Heyer was, a family friend said at Wednesday's service, "a young woman who lost her life defending the rights of others."
"I would like for us to carry her legacy on by doing the same thing: Respecting the rights of everyone," Cathy Brinkley said.
The Rev. Alvin Edwards, pastor at Mount Zion First African Baptist Church, said people should learn from Heyer that they should make each day count.
"She lived her life (in a way) that enabled her to fight for justice and righteousness," Edwards said.
As a paralegal, Heyer assisted clients through the bankruptcy filing process. She had just celebrated her five-year anniversary with the firm last week.
Wilson, her supervisor, said she easily empathized with people who would come in to file for bankruptcy protection.
"I pray and ask that (you) can somehow, some way feel the love that she had. ... She saw the good in everyone," Wilson said at the service.