Is this I Don't Want to Be Loved...?
Rihannan Alessin, a queen rotting in prison. Despaired and without hope, she drank poison and died. But… unbeknownst to her, the deity gave her a second chance at life. She was twelve again. And this time, she would live life differently. Six years later, she chooses to become Arundell’s queen… “If you’re asking me to step down from the marriage proposal, I can’t.” “Marry me and let us divorce after a year.” And this time, the time limit of their marriage would last a year. A husband she knew who was different than before… she tried not to love him again, but each time, her heart kept shaking.
The protagonist, Lianan Cheska, is a noble of royal blood. I think her hair is supposed to be white or silver, but it has a bluish tint in many panels and in the promotional art.
Her father, Count Regan Aleshin, was a low-ranking noble whose wealth and status were elevated when he married her mother, Anastasia Prebius. He never loved her mother though, and had an affair that produced an illegitimate daughter and younger half-sister to Lianan; a red-haired girl named Leticia, who was raised by her own mother away from the mansion Lianan grew up in.
When Lianan was still a young girl, her mother took her to see the Empress, whose young son, Igor, inherited the throne at the age of five, making the Empress the power behind the throne. The Empress arranged this meeting because she intended for Lianan and Igor to later marry, so that Igor could produce heirs as soon as possible and ensure that the throne wouldn't pass to a rival branch of the royal bloodline in the case of his death. Igor overheard her plotting though, and felt that she was using him as a tool.
While Anastasia and the Empress were sitting together and drinking tea, Lianan wandered off into the royal gardens and met Igor for the first time. They weren't familiar with each other at that point, but Lianan noticed a bird stuck on a nearby tree branch, and Igor saved it from an approaching cat at her request.
Some time after that, when Lianan was 12, her mother died of illness, and the day after her funeral, Lianan's father brought Leticia to the mansion to live with them.
Years later, Lianan and Igor were married as the Empress intended, but their marriage was an uneasy one, with neither one fully trusting the other.
More years passed, and Lianan ultimately wound up in prison, with Igor having turned his back on her. She was paid a visit by Leticia, who came to gloat at her predicament. She subsequently took her own life, using poison given to her by her half-brother.
She then wakes up in bed as her 12-year-old self, the day after her mother's funeral. Knowing that her father will bring Leticia to the mansion later that day, she sends for her father's lawyer, and with her now adult-level knowledge and intellect, forces him to draft legal documents enabling her to name her uncle as her new guardian, and kick her father and Leticia out of the mansion.