In a sit-down interview with Eyewitness News in Houston, the family, which included Guillen's mother, father and two sisters, spoke out about the soldier's killing.
READ MORE: 'Houston's Daughter' Vanessa Guillen's impact on Houston and Latino community
The conversation came about as part of a larger project in partnership with ABC News.
Guillen's mother, Gloria, said she wants Congress to investigate Fort Hood's handling of her daughter's disappearance.
In Spanish, she called Fort Hood leaders "clowns in a circus," and said they lied to her.
Guillen, who had been missing since April 22, was killed and dismembered by U.S. Army Specialist Aaron Robinson, a 20-year-old soldier from Calumet City, Illinois. He took his own life last week, federal and military investigators have said.
Cecily Aguilar, a 22-year-old civilian from Killeen, was arrested and charged with one count of conspiring to tamper with evidence for allegedly helping hide Guillen's body.
READ MORE: Gruesome details in report show how Vanessa Guillen may have been killed
Vanessa's sisters, Mayra and Lupe, said they won't be silent about the murder
"She was taken away from me in the most horrible way, yet they take it as if it was a joke" said Lupe. "My sister is no joke. My sister's a human being just like me, her, all of us."
They intend to continue pushing for justice and swift change on behalf of their beloved sister. They believe legislation should be passed to help sexual harassment victims in the armed forces.
"Speak about it, because we cannot let this happen again," said Lupe. "My sister was taken away. She could have been your sister, your friend."
When asked if she's been able to process what occurred, Guillen's other sister, Mayra, said she hasn't reached that point.
"I still can't accept it to be honest with you," she said. "It's been really ... like I'm dreaming, and I just don't accept it. It's been really hard."
She said if she has a daughter one day, she hopes to name her after Vanessa.
- Fort Hood soldier Vanessa Guillen's family says suspect who died by suicide was tied to her disappearance