Although the Ozera's were once among the most well-respected royal families in Moroi society, their reputation became tainted after Christian's parents willingly turned into Strigoi. This act of betrayal cast a dark shadow over the remaining family members, including Tasha.
In the beginning of Frostbite Tasha was introduced as a strong, opinionated, and passionate member of the Ozera clan who elected to remove herself from the center of Moroi society. After an incident with Christian's post-Strigoi parents, she chose to live among humans, physically train herself, and learn self-defense.
Tasha was described as having 'raven-black' hair. She had a heart shaped face with large, pale blue eyes. Like all Moroi, she had very pale skin. Her lips were described as a pale pink color. Overall she was described as having a very attractive appearance, despite having raised, purplish scars across her left cheek. Rose describes them as looking like someone had bitten into her face, tearing out part of her cheek. It's learned that, after turning Strigoi, one of Christian Ozera's parents had attacked Tasha while she was trying to protect Christian and had given her the scar. Rose comments that while the scars clearly messed her face up, they managed to complete her somehow.
Natasha was portrayed as a friendly, social and outspoken person. Her political beliefs are very much progressive; she continually pushed for Moroi to learn how to fight Strigoi; she believed that by actively helping Dhampirs fight against them, Strigoi attacks would become less of a problem. She was shown as having a very blunt nature and being brutally honest, so long as her honestly helped her to get what she wanted. Her outgoing nature led to her being a very flirtatious character, especially with Dimitri.
Despite her positive qualities, Tasha was extremely cunning and ambitious in less-than-honorable ways. She had a very self-serving nature, and her jealously of Rose Hathaway and her relationship with Dimitri Belikov brought out some of Tasha's uglier traits. Towards the end of her portrayal in the series, she was shown as desperate and violent, both actually and nearly killing several other characters. She was not above using her flirtatious nature to manipulate other to achieve certain means.
The state of Tasha's relationship with her parents and brother are ultimately unknown. However, her sadness over the fates of her brother and sister-in-law may show that they had a good relationship before they turned. She showed a moderate to high level of scorn and disapproval for most of the members of her extended family.
Christian Ozera is the son of Tasha's brother, Lucas. After willingly turning Strigoi, his parents came back to kidnap Christian. They had plans to supposedly turn him into a Strigoi after he had grown older. Tasha protected Christian and stalled Lucas and Moira until the Guardians could come to her aid. After his parents death, she became a motherly-sisterly figure towards Christian. She ultimately raised him, loved him, cared for him, and taught him whatever offensive fire magic she knew. At the end of Last Sacrifice, he frequently went to visit her in jail before her execution.
Dimitri and Tasha were initially portrayed in Frostbite as being old friends. The two were very close and got along well, and she made her romantic feelings towards him very clear throughout the story. She eventually asked Dimitri to become her Guardian in hopes of their relationship evolving into something more romantic (it's mentioned in the series that she was willing to have dhampir children to be with him). Despite his initial consideration, Dimitri eventually declined her offer. He claimed that while he believed she was an amazing woman, his heart belonged to someone else; Rose. Following his rejection, Tasha grew quietly jealous and began secretly hating Rose for taking Dimitri away from her. After Lissa brought Dimitri back from being a Strigoi, Tasha was a major advocate for his return to normal vampiric society. She eventually murdered the late Queen Tatiana Ivashkov, framing Rose in hopes that after her execution Dimitri would finally choose to be with Tasha.
Tasha and Tatiana's antagonistic relationship was primarily on a political level. Tasha was angry about the Queen's passed laws regarding the lowering of the age required for dhampirs to become guardians. She also believed that the Queen held more traditional views on the involvement of Moroi fighting and seeking out Strigoi. While part of her reasons for killing the Queen involved her desire to remove Rose from her romantic situation, she also wanted the Queen gone in hopes that the next reigning king or queen would share in her more progressive political beliefs.
When Tasha and Rose first met in Frostbite they got along with each other very well. But after finding out that Rose was the true object of Dimitri's affections and the reason that Dimitri couldn't be with her, Tasha's antagonistic feelings for Rose began to fester. With hopes of removing her from the situation permanently, Tasha framed Rose for the murder of the late Queen Tatiana Ivashkov in Spirit Bound. After Dimitri helped Rose escape and collect enough evidence to prove that Tasha had been the one to commit the murder, Rose returned to the Royal Court and called Tasha out in front of a room full of royal Moroi. In her desperation, Tasha then shot off her gun, accidentally aiming directly at Lissa's chest. Rose jumped in front of Lissa, taking the bullet for her friend instead; Tasha was immediately taken into custody following the act.