"This conservatorship killed my dreams ... so all I have is hope and hope is the only thing in this world that is very hard to kill ... yet people still try," Spears wrote, adding that her "so-called support system hurt me deeply."
In addition to noting she wouldn't perform as long as her father, James "Jamie" Spears, handles "what I wear, say, do, or think," the singer seemingly took issue with her sister, Jamie Lynn Spears, performing one of Britney's songs in a tribute at the 2017 Radio Disney Music Awards.
USA TODAY has reached out to representatives for Britney Spears, Jamie Spears and Jamie Lynn Spears for comment.
A probate judge allowed Britney Spears on Wednesday to choose her own attorney, the first big change in her case since she unloaded in court last month, condemning the "abusive" conservatorship.
The biggest revelations: Britney Spears details ‘abusive’ conservatorship in court
Judge Brenda Penny granted Spears' request to hire Mathew Rosengart, a former federal prosecutor, to represent her in the pop star's ongoing effort to be freed from her 13-year conservatorship, under which she has little control over her finances or important life decisions.
Spears, 39, who dialed into the hearing, spoke for about 15 minutes and became emotional, saying she wants an "investigation" of the alleged abuse.
She also reiterated that she wants her father out as a co-conservator, and that she refuses to undergo more medical assessments, which she called "stupid psych tests."
"I’m not willing to sit with anybody at this point to be evaluated,” she told the judge. "I want to press charges for abuse. Instead of investigating my capacity, I want an investigation on my dad."
Britney Spears posts '#FreeBritney':The pop star won right to hire lawyer in conservatorship case
In her Instagram post, the pop icon said she would "much rather share videos" online of herself dancing in her living room than "onstage in Vegas."
"Look I'm not gonna be performing on any stages anytime soon with my dad handling what I wear, say, do, or think!!!! I've done that for the past 13 years," she wrote. "I'm not gonna put on heavy makeup and try try try on stage again and not be able to do the real deal with remixes of my songs for years and begging to put my new music in my show for MY fans ... so I quit !!!"
"Hope is all I have right now," Spears concluded, calling out those who criticized her latest dancing video in comments. "You're lucky I post anything at all ... if you don't like what you see, unfollow me !!! People try to kill hope because hope is one of the most vulnerable and fragile things there is."
This month, Spears' longtime manager, Larry Rudolph, reportedly announced his resignation in a letter to her conservators, citing the pop icon's intent to "officially retire" from music.
Rudolph told her father and Montgomery that he was resigning because he “became aware" of Britney's unhappiness and disinclination to perform under the conservatorship.
The letter was published by Deadline and The Wrap. In it, Rudolph said Britney Spears told him in 2019 that she intended to take an “indefinite work hiatus,” and now that she’s reiterated that desire, she no longer needs a manager.
In January 2019, Spears abruptly suspended her Las Vegas residency because of her father's health issues. She has not performed since.
Last year, she released a deluxe version of her 2016 album, "Glory," which included a new single featuring the Backstreet Boys.
Contributing: Maria Puente and Bill Keveney
This article originally appeared on USA TODAY: Britney Spears slams Jamie Lynn Spears, dad Jamie in conservator fight