Her estranged husband, Armando Perez, 38, is the accused killer, but he is still no where to be found.
For family members, it has been a torturous year.
"Everyday we light a candle next to her picture," Janette Gonzalez told NBCSanDiego about her sister.
But while some say time can heal the deepest wounds, they certainly haven't healed for Janette and her parents.
On October 12, 2010, Diana, 19, had just given birth to her daughter Crystal months earlier. She was studying to be a nurse when San Diego police say she was stabbed to death inside a bathroom at San Diego City College.
Homicide detectives called it one of the most horrific crime scenes they had ever seen.
Investigators quickly pointed the finger at Perez, but he disappeared in Mexico where he is believed to be still hiding.
"He has to pay for what he did,"said Janette.
Diana's family members are also still very angry with the District Attorney's office.
A few weeks before her murder, Perez was accused of kidnapping Diana, and then beating and raping her for three days.
But prosecutors declined to take the case, citing a lack of evidence.
Janette believes Perez should have been charged.
She is hoping someone will come forward with information leading to an arrest.
Because Diana was murdered on a Tuesday last year, the candlelight vigil is set to begin at 6 p.m. on Tuesday at City College.
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