Caterina is a sharpshooter from a long line of law-bringers: her great-great-great-great-grandfather formed the settlement of Roca-Lomada in New Mexico, and her father had served as the town's sheriff since before she was born. Guillem "Gill" Nievez was an expert gunman and skilled survivalist, both qualities he passed on to his two daughters, whilst her mother was a former caravan guard who had settled down with Caterina's father. Caterina's parents both stressed the importance of empathy and one's responsibility to the community they lived in, and were big believers in the rule of law. Unlike many who saw the expansion of the New California Republic across the south-west coast as a worrying development, Caterina's parents believed that the arrival of an egalitarian military could only have a civilizing effect on the desert.
Her older sister Adelia would go on to succeed their father after his retirement, bringing peace and prosperity to Roca-Lomada for years to come, but Caterina had evidently inherited her mother's sense of wanderlust. She enlisted in the NCR as soon as she was able, where her unique talents and rural upbringing made her a natural fit for the NCR's Rangers division.
As the rest of the NCR forces prepared to dig in along the Colorado River, in 2260 Caterina and her fellow Rangers were deployed south to protect what was by then known as the Mexican "frontier". Under the leadership of veteran Ranger Hanlon, they responded to a call from the beleaguered settlement of Rattletail, who were allegedly being terrorized out of their homes by a criminal faction. It was only after a multi-night siege that the Rangers discovered that the "raiders" the settlers had been killing were actually innocent locals, trying to access the town's well. Fearing for the safety of its residents - not to mention the damage done to the NCR's public image if the mistake were found out - Hanlon made the decision to elide the incident in the official reports, an act which the nineteen-year-old Caterina took particularly vocal exception to.
Nonetheless, Caterina continued to serve with the Rangers for several years without incident, though her relationship with Hanlon never recovered even after the veteran Ranger was promoted to Chief. It was only after the massacre at Bitter Springs that Caterina and Hanlon had their final, very public reckoning, resulting in Caterina being dishonorably discharged from the NCR military. The act cost her everything: her entire life was bound up in her service, and, with the majority of settlements still under NCR control, she struggled to find honest work as a result. She eventually took a part-time job delivering packages with the Mojave Express, slowly building a new life for herself as a wasteland courier.
Whilst on a high-priority delivery between southern California and the New Vegas strip, she was ambushed by a group of raiders just outside the town of Goodsprings. Led by their mysterious, smooth-talking commander, Catrina's attackers shot her in the head and dumped her in an unmarked grave. She was found and nursed back to health by the people of Goodsprings, although the incident had a permanent effect on her. When she had healed enough to report for duty at the Mojave Express, Caterina discovered that the business had been hit in her absence, with many of her colleagues murdered by the same people that had left her for dead.
Caterina's attempts to report the crime to the local NCR troops fell on deaf ears due to the ongoing war effort and, frustrated by their lack of interest, she decided to hunt down her attackers herself. At the time, she told herself that she was simply gathering information in order to pass on to the NCR. However, it soon became clear that Caterina had stumbled into something bigger and more complex than she had anticipated. Her search took her across the wasteland and into the depths of New Vegas, where rival factions vied for the heart of the Mojave and a mysterious platinum chip, which was apparently worth killing for. Having witnessed the brutality inflicted by these uncaring factions first-hand, Caterina begins to wonder: who is qualified to dispense justice, if not the NCR?
A note on Ships: Caterina/Veronica is about as close to an OTP as I'm likely to get - the pair of them are supportive, communicative, and basically an example of what a healthy relationship should be (as opposed to their relationships with their respective factions, which are the picture of dysfunction). Point of note, Caterina does meet Veronica's ex-girlfriend Christine Royce during the Dead Money DLC, and the pair have what I can only describe as a short, bittersweet romance, before they're called away by their respective vendettas. Given the history between the three of them, Caterina/Christine/Veronica is definitely a pairing I'm interested in for a potential post-game "fix-it" scenario. Caterina has Capital-H-History with Col. Cassandra Moore, who served alongside her in the Rangers, but is now the war hawk commanding officer in charge of the NCR forces at Hoover Dam.