"I’m so proud of my sister! She did so good on Dancing With the Stars ⭐," the mom-of-two, 42, captioned the upload, which featured a photo of Jamie Lynn, 32, dressed in costume.
The timing of the "Toxic" singer's post is odd given that even though the Zoey 101 alum returned for the Season 32 finale — which aired on December 5 — she was eliminated in early October during the second week of the competition.
However, Britney's post may have been her way of showing the public that they're making amends, as an insider claimed the two women are now "speaking" after years apart.
In Britney's memoir, The Woman in Me, she alleged that one of the reasons for their turmoil was that Jamie Lynn did nothing to help her escape their father's strict 13-year conservatorship over the pop star.
"As I was fighting the conservatorship and receiving a lot of press attention, she was writing a book capitalizing on it," Britney wrote of how her sister allegedly ignored her cries for help and instead shaded her in her own book, Things I Should Have Said. "She rushed out salacious stories about me, many of them hurtful and outrageous."
While the state of the girls' relationship remains murky, Britney made it clear she's on better terms with her mother, Lynne Spears, who came out to celebrate her eldest daughter's birthday earlier this month.
The Crossroads actress' hairstylist Baihly B even shared a photo of the singer cuddled up with Lynne, 58, on the couch.
"Happy Birthday to you @britneyspears I am so happy you and your Momma are together at last," Baihly B wrote. "Here’s to healing and a life of happiness, freedom and bonds that will never be broken!"
One insider said of the reunion, "They were two peas in a pod."
The meet-up came less than two months after the "Overprotected" vocalist complained in her memoir that her mother tossed away her childhood possessions — something Lynne denied via social media.
"@britneyspears I'm not sure who told you I got rid of your dolls and journals but I would never do that! That would be cruel because I know how much they mean to you," Lynne wrote alongside pictures of the childhood items on November 9.
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"They are special to me too because of the years we spent collecting them," added the mother-of-three. "Of course I still have your things, and I am happy to send them to you if you'd like me to. Please let me know and know how much I love you!"
Page Six reported that Britney and Jamie Lynn are speaking again.