Texas City ISD reserved that spot in memory of Brandy Vela, a high school senior who committed suicide last year after police said she was the victim of cyberbullying. Two people were arrested, charged with unlawful disclosure of intimate visual material and online impersonation, among other charges.
Brandy would have graduated Friday, along with the rest of her Texas City High School Class of 2017.
"Going to school, it's hard, it really is," said Michelle Vela, Brandy's younger sister. "No one really knows what you feel."
The Vela family placed flowers and graduation balloons at Brandy's grave Friday morning before the ceremony.
Brandy's father Raul hopes the empty seat at the graduation ceremony will remind people to be kind to each other and to pay close attention to unusual behaviors in loved ones.
"I could tell certain things about Brandy, you know, she was very beautiful, she loved makeup," Raul said. "She would spend hours in front of the mirror. And I do remember the last couple of weeks that she would just throw her hair up in a knot and go. That wasn't Brandy before."
Michelle channeled her sister's love for makeup as she got ready for her role as an Honor Guard in the graduation ceremony.
"She fought a lot," Michelle said. "I want people to know that there's something else you can do, you know, we're here for them, the family is here for them."
Brandy, 18, tragically committed suicide in November after enduring several months of relentless cyberbullying, stalking and harassment, according to police.
Texas City police arrested Vela's ex-boyfriend and his current girlfriend in March.
Police say 21-year-old Andres Arturo Villagomez and 22-year-old Karinthya Sanchez Romero, both of Galveston, were behind the harassment.
Villagomez has been charged with unlawful disclosure or promotion of intimate visual material. Romero was charged with stalking and online impersonation.
The teen, who was described by her school as well-liked and friendly, was buried December 7. By the next day, someone had opened a social media page in her memory, but it was quickly filled with disturbing posts about her; the cyberbullying literally following her to the grave.
"Two days after her funeral, somebody opened up a social media page in her name," Paul Vela said. "And people thought the family did it, so it started with people putting sincere condolences. After a few minutes, either four people or the same person posting four times said some things harassing Brandy about being a big fat cow, writing 'you finally did it' with a picture of a gun, writing 'you're a coward,' 'you should have done this a long time ago,' some really horrific things."
One of the posts shows a smiling Brandy with the words "my face when you shoot yourself in front of your family." Another post showed a stick figure holding a gun with the words, "oops am I dead?" A third shows a gun hidden inside a book.
"People are more likely to write horrible things when they think they're being anonymous," said psychologist Susan Swearer, co-founder of the Bullying Research Network. "From a psychological perspective, people who write horrible things about other people, particularly after they've passed away, they have their own mental health issues."
She says Paul Vela did the right thing by reporting the social media pages to authorities.
"When people feel emboldened to write mean and hurtful things about other people, they'll just extend it to siblings or families," Swearer said.
Vela, whose family was avoiding social media in the wake of Brandy's death, said the posts were first brought to their attention by friends.
Shortly after the news of Brandy's death broke, people also began attacking Paul Vela online, he said.
"People were putting comments about me, saying that I should have done something different, so I blocked it all. I'm not reading it anymore," he said.
CNN contributed to this report.