Arianna first appears in Days of our Lives when Caroline Brady hires her as a waitress at the Brady pub. She then moves to Salem. Soon after starting her job, Arianna reconnects with her older brother, Rafe Hernandez, who she has been estranged from. She meets Rafe's girlfriend, Sami Brady, and takes an instant dislike to her after she learns that Rafe resigned from the FBI for her. Arianna meets recovering drug addict Brady Black and takes a liking to him, but refuses his offer of a date. She explains that she has been in relationships with drug addicts in the past and does not want to again. Arianna later agrees to a date with Brady and they have a picnic in the park. They then begin a relationship. Arianna uses the pub as a front to receive drugs and then sell them. Arianna meets Roman Brady and is revealed to be working undercover for Salem Police Department to find the root of drug distribution in Salem. Victor Kiriakis learns that Arianna is one of his dealers and forces her to end her relationship with his grandson Brady. She asks Roman if she can leave the investigation, but he does not. As time goes by EJ DiMera finds out that Arianna is working for him and he soon begins to favor Arianna over Troy due to her selling more drugs then Troy. Jealous of Arianna moving up the ladder in the drug cartel and EJ warning Troy, Arianna would take his spot, Troy his a hitman to kill Arinanna. Due to Mickey Horton's death, one day the Pub is closed but Arianna decides to inventory that day. Troy who had been watching the pub calls the hitman to take out Arianna. The hitman sneaks into the pub while Arianna is doing inventory and tries to rob and kill Arianna, but Brady who chases him off. After the hit fails Troy decides to take matters into his own hands and to kill Arianna himself. Troy breaks into the pub when she is alone and sneaks into her room to kill her, however EJ who had come by to thank Arianna for her kind words of encouragement earlier that day arrives saves her from Troy. Troy is arrested for attempted murder and Arianna is taken off the investigation but not before Troy notices Arianna speaking to Roman and realizes she is working undercover, he warns EJ that Arianna is a snitch.Brady who is also at the police station asks EJ what Troy is talking about and EJ pretends to have no idea what Troy is talking about and denies he has ever met Troy. After this the drug cartel storyline is dropped.
Brady proposes marriage and Arianna accepts. They travel to the Dominican Republic to marry, but Brady's ex-girlfriend Nicole Walker follows them and attempts to reconcile with Brady. However, he refuses as he loves Arianna. A tropical storm stops the ceremony from taking place and they return to Salem. Nicole discovers that Dr. Richard Baker is an associate of the Salem Mugger, who has been mugging several high profile men. She makes him plant Arianna's hair at the crime scene. Arianna is then arrested and charged with multiple crimes. As she protests her innocence, Brady does not believe her and she ends their relationship. Lawyer EJ takes over Arianna's case and looks for evidence that Nicole framed her. Hope Williams Brady later confesses to the crimes after being under the influence of sleeping pills. Arianna overhears Sami confessing to shooting EJ and decides to tell him. She tells Rafe, who reveals that he already knows and supports Sami. Arianna agrees to meet with Sami to hear her side of the story. Sami explains why and when she shot EJ and Arianna video tapes her confession. After Arianna tells Sami that she is going to the police, Sami attacks her but she escapes. Sami calls her son Will Horton and Rafe, telling them to stop Arianna. Will finds her at the pub and stops her telling EJ. Arianna runs away from Will onto the road, where she is hit by a car. Days later she dies in hospital from complications of the accident. After her death, Arianna's ghost haunts Sami with the truth about EJ's shooting