A judge sentenced her to 19 years and four months to life in state prison for the 2022 fentanyl murder of Jade Dreith.
"This is completely avoidable, and that's what's so frustrating for me as a judge," Fresno County Superior Court Judge Alvin Harrell III said.
Gonzalez has been convicted of murder for nearly a year.
Last March, a jury sided with prosecutors in a first-of-its-kind case, agreeing that Gonzalez sold the fentanyl that killed Dreith even when she knew it was deadly.
"Jade didn't poison herself. She didn't want to die," the victim's sister, Sage, said. "Death was brought to her by Cassidy Marie Gonzalez."
Sage believes Gonzalez used Jade's kindness and their friendship to kill her.
"You looked at a person who trusted you, and you decided her life was worth less than your comfort, your impulses, and your habits," Sage said.
Through it all, Gonzalez has denied wrongdoing.
On Friday, her mom tried to cover, saying the case was motivated by unfair connections to the District Attorney's Office.
"The power that they have. The people that they know, that's why we are here today," Gonzalez's mother told the judge. "That's why my daughter's in this situation."
"Stop," the judge replied.
"This has nothing to do with influence (or) favor," Judge Harrell III said. "It has to do with the rule of law in the state of California."
Gonzalez, who was largely unmoved through it all, broke down as she offered an apology, promising to get counseling in prison.
The victim's sister called it an act.
"I see your self-pity and your terrible little tears. I don't see a victim at all," Sage said. "I see someone who took a life and then expected to get sympathy for the consequences."
For news updates, follow Gabe Ferris on Facebook, Twitter and Instagram.