Originally thought to be Cal Winter's daughter, blood tests proved Jeannie to be Shane's daughter. Jeannie lived with her mother in California.
In July 2013, Jeannie arrived back in Salem. However, she had started going by her middle name, Theresa. After overhearing J.J. and his friend Rory discuss their marijuana stash, Theresa approach J.J. and started flirting with him in hopes that he would share some of the drugs with her. The two continued their flirtation, despite both their age difference and an unpleasant run-in with Jennifer at the Horton house. Theresa became one of J.J.'s customers as well, buying marijuana and requesting cocaine from him.
Both were shocked to find themselves in Jennifer's office one day. J.J. was there to see his mom. Theresa was there to start her new job as a PR assistant at Salem U Hospital. Kayla explained that Theresa was her nice, whom Jennifer had agreed to hire as a favor to Kayla. Jennifer was not pleased to find out that she'd hired the woman she found with her underage son earlier in the week. But Theresa insisted that they were just friends and that she liked older men.
The statement proved to be true when Theresa took an interest in Daniel Jonas. She tried to flirt with him, but he did not return her advances. She briefly flirted with Nick Fallon, but changed her mind when she heard that he might not have any money. Finally, she set her sights on Vargas.
Vargas and Theresa went on a date to the opening of Club TBD in Salem. She arrived at his house to pick him up and saw him taking money for the night out of a coffee can in the kitchen. She learned that he had been in prison, but was not phased. He had some cocaine for the night which the two shared at the club. But, when Vargas got a little too high, Theresa started flirting with a handsome stranger. Vargas saw them and started a fight with the man. Vargas was arrested and sent back to jail. But before he went, he told Hope that the cocaine in his pocked belonged to Theresa Donovan.
Hope went to Theresa and confronted her with the news. She also told Theresa that she knew about Theresa's arrest record in California. Hope asked Theresa to go to rehab, but Theresa refused. Instead, Theresa embezzled money from the hospital's PR discretionary fund to cover some of her drug expenses. Jennifer found the check and fired Theresa on the spot.
Determined to pay Jennifer back for costing her a job, Theresa set her sights on Jennifer's ex, Daniel. Theresa worked the rumor mill at the hospital to spread the word that Daniel was sleeping with Theresa. However, in reality, Daniel had turned down Theresa's advances cold because he was still in love with Jennifer. Hurt by Daniel's rejection, Theresa turned her attention to Jennifer's son, J.J.
Theresa invited J.J. over to her apartment. The two drank and smoked marijuana together. They started to kiss and Theresa suggested that the take ecstasy before having sex. J.J. didn't want to take his does, so Theresa drank it on top of her own. She passed out. J.J. grabbed her phone and saw that the last call she made was to Daniel. So, he called Daniel for help.
Daniel arrived and told J.J. to sneak out so that no one would see him. (J.J. was currently on probation from a judge and if he was caught with drugs, he'd go to prison.) Then, Daniel took Theresa into the shower to wake her up and called 911. He rode with her to the hospital to see that she would recover from his overdose. When Theresa woke up, she said that she couldn't remember anything that happened surrounding her overdose.
The entire Brady family was worried about Theresa. Shane and Kimberly flew back from California to see her. They were worried that leaving Theresa in Salem was a bad idea. Theresa swore that she'd changed and was done with drugs and lying. Shane and Kimberly believed her and left her with their blessing to stay in Salem.
Theresa seemingly took steps to make herself better, including talking to Maggie about attending NA and apologizing to Daniel. But the truth was that Theresa remembered everything that happened that night and was just pretending to have amnesia in order to drive a wedge between Jennifer and Daniel, thus making Jennifer's life worse.
When J.J. finally confessed to Theresa that he was the one who was with her the night that she overdosed, she laughed at him and told him that she was faking all along. J.J. was furious with her and wanted to tell everyone that it wasn't Daniel with her when she overdosed. But, Theresa showed J.J. a video she made that night of J.J. smoking weed. She threatened to send the video to the judge if J.J. didn't do exactly what she said. (J.J. was on probation, awaiting a formal sentencing from assault and disturbing the peace charges.) So, she send J.J. on various errands to get drugs for her.
To keep up the ruse of someone who had overdosed and was trying to change, Theresa started attending AA meetings. She met Brady Black there, and the two immediately butted heads. But, eventually, their relationship turned flirtatious. Theresa could tell that Brady wasn't serious about AA, so the two would meet to drink together. Theresa was drawn to Brady and jealous of his rich lifestyle.
J.J. knew that he needed to do something to stop Theresa. So, he arranged for her to find a hospital check that was made out to Abigail. Theresa hired a guy to produce a fake hospital ID that identified Theresa as Abigail. Theresa took the check and her fake ID to an office supply store and bought debit gift cards, claiming they were for an employee incentive program. As the clerk grabbed the debit gift cards and rang them up for her, J.J. entered the store, surprising Theresa. He informed her that the clerk was actually a friend of his and her whole scheme was caught on the store's security cameras. He told her that they were even -- she couldn't release the video she had of him without him releasing the one he had of her. Theresa was furious.
Theresa blamed Brady for her lapse in judgement. She'd been so enamored with his wealth that she'd let her own guard down. But, that didn't stop her from pursuing a romantic relationship with Brady. She also kept sights on getting revenge on Jennifer, through Daniel.
She tried to play the victim card with Daniel, asking him to please tell her what happened the night he overdosed. But, Daniel kept pushing her away. She stole his keys from his locker one day and made a copy of his house key. She didn't know how, but she thought it would come in handy.
Worried that his mom and Daniel were still not back together because everyone thought that Daniel had slept with Theresa, J.J. decided to come clean. He told him mom everything, including that Daniel had been covering for him this whole time. Theresa went to Daniel and gave him one last chance to sleep with her before she released the tape of J.J. But, J.J. arrived at Daniel's apartment just in time and told Daniel about the video he had of Theresa. Daniel kicked Theresa out of his apartment and told her to stay away from him, J.J., and Jennifer.
When an embarrassing fake photo of Jennifer circulated around the hospital and unflattering comments about her flooded the hospital message board, Daniel and Jennifer assumed that it was Theresa. But, Theresa turned her attention towards Brady. She liked that her relationship with Brady bothered Maggie, Jennifer, and Daniel. Soon, she grew fond of Brady too, enough to turn down Liam Frazer's advances when he seemed to take an interest in her. But, one day at lunch with Liam, a picture of Jennifer fell out of his wallet. Theresa knew right away that Liam was obsessed with Jennifer and was behind the recent photos and messages.
Theresa ran to find Daniel to tell him about Liam. But, when Daniel found her, he didn't let her speak and immediately accused Theresa of sending the photos and messages. Theresa tried to tell him otherwise, but Daniel wouldn't listen. He threatened to have her fired from the hospital. Furious, Theresa went back to Liam and offered him the key to Daniel's apartment. Liam took it.
A few days later, Daniel arrived at the hospital to perform a surgery. But, a few minutes into surgery, Daniel had to leave. He collapsed and was hospitalized. Toxicology reports showed that he was high on opiates. Daniel was put on temporary suspension, per hospital policy, while the investigation took place. Daniel and Jennifer immediately suspected Theresa. Theresa knew that Liam was behind it.
Theresa tried to do damage control, begging Brady to believe her that she had nothing to do with what happened to Daniel. Brady said that he wanted to believe her, but if he found out otherwise, she'd be sorry. Brady agreed to help Jennifer find out what happened to Daniel. To do so, he told Theresa that he had to stop drinking and seeing her. Theresa was crushed.
Liam eventually followed Jennifer out to Smith Island and held her captive. While he ended up dying in the struggle, Liam did confess to Jennifer that he'd been behind the pictures, message boards, and drugging Daniel. Since Anne was the only person who knew that Theresa gave Liam the key to Daniel's apartment, Theresa thought that she was in the clear. She frequently reminded Brady, Daniel, and Jennifer that they were wrong to accuse her of drugging Daniel. She and Brady resumed their relationship.
All of Brady's family told him that a relationship with Theresa was a bad idea. But, he kept spending his time with her, engaging in heavy partying that included cocaine. Eventually, he told Theresa that he wanted more from their relationship. Theresa was thrilled because this meant her plan to get his money would be easier.
The two of them took a private jet to Vegas. Brady drank heavily and Theresa had to carry him out of the casino. As a passed-out Brady and Theresa flew home on the Titan jet, Theresa looked down at the new weddings rings on their hands.