Daniel Gross and Melissa Leonardo, both of Modesto, are suspected of stabbing Cuesta several times, tying her up and leaving her body on Tesla Road in Livermore.
Cuesta was flown to a nearby hospital, where she died. Investigators say Cuesta used her final words to identify her killers.
"This victim really tried to survive, and she fought and she fought," said Sgt. Ray Kelly with the Alameda County Sheriff's Office. "The last thing, we believe, that she was able to do was to point us in the direction of the people that killed her. And that's pretty remarkable."
Richard Loadholt was carpooling to work with three other friends for an early shift at UPS when they found Cuesta. He told FOX40 the young woman was in such bad shape he couldn't make out the color of her hair.
"She laid down for almost three minutes at one period, and we told her to get up. She knew she had to get up and I commend that," he said.
She was "always positive"
FOX40 spoke with Cuesta's father through Facebook Tuesday. He said his daughter was a warrior and lived long enough to get justice.
Alex Yanez tells FOX40 that Cuesta was a very positive woman and a determined skateboarder, who would frequent El Pescadero Skate Park in Tracy.
"Guys fall just as hard and won't get back up and sit rest of the day. She would fall and get right back up and try it," Yanez said. "If she wanted that trick bad enough she would get it."
Yanez shared pictures of Cuesta with FOX40, describing his friend as a happy, smiley teenager.
“Whenever Liz came to this park, ‘Oh, there’s Liz!’ You know, always positive, I would look forward to seeing her,” he said.
FOX40 also spoke with another one of Cuesta’s friends over the phone. She asked to hide her identity for privacy reasons.
"Really outgoing. She was, like, always down to earth and I never spent a day with her being sad," she said.
Friends were unable to share how the suspects and Cuesta knew each other. Yanez explained that, up until weeks ago, he would see her around the skate park. But the 19-year-old got involved in some sort of argument and stopped showing up.
“I just want to know why they did it, like, what was so bad?" Cuesta's friend said. "Like what could she have... she was the nicest person. What could she have done?”
“She’s strong enough to walk to that road and get her instant justice, and I hope those people never see the light of day again," Yanez said.
Loved ones hosted a private vigil in San Jose, where the 19-year-old was originally from. A GoFundMe has been set up to help Cuesta's family members.
Tales of jealousy and anger
According to Gross and Leonardo's social media accounts, they are engaged.
FOX40 spoke with Montana Howland, who considers Leonardo his sister, and Misty Dawn Grasty, who grew up with Gross and used to live with him as a child when their families were both in the same sober living house.
"He was an angry person but I don't think he would take it out on other people," Grasty said.
"She has emotional issues but she would not physically hurt someone else," Howland said.
They were trying to understand how the couple could have left Cuesta for dead.
Grasty said Gross had a rough childhood but internalized his emotions.
"Like he would cut himself," she said.
She said Gross was always the odd one out, but that his fiancee was extremely jealous.
"She actually got physical with him inside of a store for looking at another female," Grasty said.
Grasty told FOX40 people who know the couple think that jealousy could have been directed at Cuesta. But Howland said he video chatted with her from Kansas just days ago. He said she mentioned Gross talking to another girl, but it was a joke.
Howland believed Gross to be the only one capable of such violence.
"Daniel has always talked about if someone pisses him off bad enough he will kill them," Howland said. "But Melissa is the only one with a car and she goes everywhere Daniel goes, so that's probably the reason she got (dragged) into it."
Howland told FOX40 he knew Leonardo owned a lot of knives, but only as collector's items. He didn't think she would ever use them to stab someone.
"I just know my sister willingly would not kill someone without someone mentally controlling her mind," Howland said.
Neither of their friends had ever heard of Cuesta, but they both want to know the truth as much as Cuesta wanted to tell it.
"She wanted justice for herself, and she's really brave for that," Grasty said.
The suspects will have their first court date Wednesday.