Ilia is a former member of the White Fang.
Ilia was originally born and raised in the Mining community of Faunus laborers likely working for the SDC in Mantle.With Ilia herself having likely spent a majority of her childhood growing up their together with her parents in the community of Miners who mined dust for the Kingdom.
Eventually after putting their resources together and their savings,her parents eventually managed to Enroll Ilia in an Atlas Prep school,directly in the Kingdom's Capital of Atlas ,greatly delighting Ilia due to now living in the "City Of Dream" and having felt like a "Princess" while living and studying there.
Eventually due to wanting to fit in with the Upper Class classmates from the city,Ilia began to hide her Faunus heritage and slowly began to join her classmates in their racism and bigoted opinion and commentary in insulting the Faunus due to feeling and believing she was "one of them".However her opinion of the Upper Class of Atlas changed for the worse upon her parents deaths in a mining accident,upon hearing of the cruel words and snickering her classmates expressed upon hearing the deaths of the miners,Ilia bursted into a rage fueled by guilt and grief and physically assaulted them due to their cruelty and apathy to the sufferings of the Faunus and since then her opinion of Atlas's upper class has taken a severe down spiral ,as seen where she now holds no reserve or remorse in actively assisting the White Fang in their various terrorist attacks and operations to "better" the Faunus place in the world by attacking Atlas operations and facilities to assist in their revolution.
As her parents were one of the many miners working for the SDC,Ilia likely did not have a good opinion on the Company due to their controversial Labor laws and policies and upon their Deaths in a Mining Accident owned by the SDC, Ilia's opinion on them has seemingly worsened.
Later upon joining the White Fang,Ilia was seen assisting Sienna Khan and Adam Taurus in attacking one of their Facilities in order to "help" Faunus rights showing that she had now issue attacking the company to assist in advancing the Faunus race.However it is shown that despite being committed to their goal,Ilia is still shown to be uncomfortable with the excessive violence employed by members of the Fang,where it was seen that despite having a low opinion and dislike for the company Ilia took no pleasure in seeing its employee's suffering,as seen when Ilia had a look of pure sorrow and sadness at seeing Sienna and Adam brutally attack the SDC guards and later showed a look of disgust at Adam's obvious bloodthirst and pleasure at him attacking them.
Ilia's exact relationship with her parents is unknown,but before their deaths they were noted by their daughter to have loved and cared for her deeply. Hoping that Ilia's future would be far better than their own lives,they has pooled together all of their life savings in order to enroll her in a prep school in Atlas,hoping to give their daughter a better advantage to succeed life and give her all the benefits that they never had. Knowing of the strong racism and bigoted beliefs the Atlas Elite possessed in regards to Faunus,They gave her a strict set of rules to hide her Faunus heritage, showing their desire for her to live a normal life free of discrimination and hoped that their daughter's friends would genuinely see and love her for herself. When they died along with several other Faunus in a mining accident, the news eventually reached Atlas and eventually reached Ilia and her friends,who then began belittling,laughing and snickering at the news,clearly delighted upon hearing the news of the "animals" dying,this in turn caused their daughter to react in severe grief and eventually revealing her Faunus nature as she openly cried over their deaths and turned blue, greatly scaring her "friends" and causing the young faunus to then physically assault them for their cruelty,breaking their teeth in anger.
In "True Colors", Blake Belladonna asks Ilia if her actions within the White Fang are what her parents would have wanted, causing Ilia to break in tears and say that she does not know what else to do. This, along with Ghira Belladonna saving her from death, causes Ilia to decide to leave the White Fang and help Blake defend Haven Academy.
Through the White Fang, Ilia is brethren with the two fox Faunus. They know her well enough to be aware that she has a history with Blake Belladonna and informed her of Blake's return. In "Welcome to Haven", according to Blake, they blamed Ilia and they were disappointed that she is working for Adam. However, they were revealed to have already been collaborating with her prior to this and after she had her Scroll taken. Later in "Necessary Sacrifice", the brothers assign Ilia to assassinate Ghira and Kali Belladonna and bring Blake alive to Adam Taurus, much to Ilia's dismay. She eventually betrays them after losing her will to fight.
Though they have not interacted onscreen, Ilia knows much about Adam's plans. She stored such information in her Scroll before Blake seizes it in "Two Steps Forward, Two Steps Back".
Later, in "Unforeseen Complications", Ilia denounces the Belladonnas for speaking out against Adam and proclaims only he can give the Faunus the future they desire.
In "Alone Together", Ilia admits she was jealous of Adam because of Blake's attraction to him. However, following Blake's departure, Ilia dismisses these feelings in order to pursue Adam's ideals. However, she later betrays the White Fang after Blake persuades her.Volume 6 Adam Character Short", it is shown Ilia working together with Adam and Sienna in infiltrating an SDC facility and assisting them from the sidelines in their mission, showing a degree of teamwork between the two. However it is also shown that despite working together in the same side, Ilia still harbors reservations, guilt and discomfort at the excessive violence against humans employed by Adam during their missions, as seen when Ilia had a look of disgust, sorrow and guilt at the obvious pleasure Adam was taking in attacking and fighting the clearly outgunned Human Guards.
Ilia and Blake are both comrades from their old White Fang days and close friends. Ilia also holds romantic feelings for Blake, which she professes to Blake in "Alone Together", and is upset they were unrequited.
During the period between Blake's departure from the White Fang and Ilia's departure from the White Fang, Blake and Ilia are somewhat unwilling enemies. Blake wants to stop her from becoming like Adam while Ilia wants to further the goals of Adam's White Fang under the orders of the Albains. Ultimately, after Blake tells Ilia that her ways go against the wishes of her parents and Ghira saves her from certain death, Ilia betrays the White Fang and joins Blake.
In "Argus Limited", although she is saddened that Blake is leaving Mistral with her friends to Altas, she respects her decision. Ilia gives Blake an embraced and thanks her for everything before they go their separate ways.
The two first meet with an immediate confrontation when Sun and Blake catch Ilia spying on them. In "Two Steps Forward, Two Steps Back", she wounds and renders Sun unconscious with Lightning Lash to prevent him and Blake from pursuing her. Later, in "Unforeseen Complications", Ilia evades capture by Sun when she interrupts Ghira's press conference.
In "True Colors", Sun fights Ilia during the house-fire, and she keeps to defending herself. At the end of the attack on the Belladonnas, Ilia seeks redemption when she incapacitates Corsac, and when she and Sun finally evacuate, they have dejected looks. Ilia asks to join Blake to save Mistral, which earns Sun's forgiveness. He playfully pinches her arm to get even with her for stabbing him, which she apologizes for.
Neptune appears to have some romantic interest in Ilia, going up to and flirting with her, though he is unaware of Ilia's homosexuality. Ilia has a confused look on her face when he mentions he did not know she would be around.