Spears, a singer, actress and the younger sister of Britney Spears, spoke out Monday on Instagram Stories after Britney Spears asked a judge last week to end the 13-year conservatorship headed by her father, Jamie Spears.
Spears said she hadn't spoken out until now because she felt Britney Spears "was able to speak for herself" but that she's "only loved, adored and supported" her sister since the day she was born.
"I don't care if she wants to run away to a rainforest and have a zillion babies in the middle of nowhere, or if she wants to come back and dominate the world the way she has done so many times before, because I have nothing to gain or lose either way," Spears said. "This situation does not affect me either way, because I'm only her sister who's only concerned about her happiness."
Spears said she's always made a "very conscious choice" to "only participate" in Britney Spears' life as a sister.
"I've paid my freakin' bills since I was 10 years old. Not that I owe the public anything, because my sister knows I love and support her. That's the only person I owe anything to," she said. "I'm not my family. I'm my own person, and I'm speaking for myself."
Spears said she's "so proud" of Britney Spears for speaking out and requesting new counsel.
"If ending the conservatorship and flying to Mars or whatever the hell else she wants to do to be happy, I support that 100 percent because I support my sister," she said. "I love my sister -- always have, always will. As long as she's happy. So let's keep praying. That's all."
Britney Spears addressed the "abusive" conservatorship during her testimony last week, alleging she was forced to go on tour and perform her Las Vegas residency, placed on lithium against her will, and prevented from removing an intrauterine device so she can have another child.
Aguilera, who starred with Britney Spears on The Mickey Mouse Club and rose to fame as a pop star at the same time as the singer, voiced her support for Britney Spears Monday on Instagram Stories.
"These past few days I've been thinking about Britney and everything she is going through. It is unacceptable that any woman, or human, wanting to be in control of their own destiny might not be allowed to live life as they wish," Aguilera wrote.
"To be silenced, ignored, bullied or denied support by those 'close' to you is the most depleting, devastating and demeaning thing imaginable. The harmful mental and emotional damage this can take on a human spirit is nothing to be taken lightly. Every woman must have the right to her own body, her own reproductive system, her own privacy, her own space, her own healing and her own happiness," she said.
Aguilera said she believes Britney Spears has been "living without compassion or decency from those in control" and that the singer "deserves all of the freedom possible to live her happiest life."
"My heart goes out to Britney. She deserves all the TRUE love and support in the world," she said.