The 40-year-old performer has published a lengthy social media post about her sister's media presence this week.
Britney Spears has called out her sister Jamie Lynn for capitalising off of her 13-year conservatorship.
Earlier this week, Jamie Lynn appeared on 'Good Morning America' to talk about her upcoming memoir 'Things I Should Have Said'. The actress, who starred in 'Zoey 101' from the age of 14, said in the interview that at the time of her sister's conservatorship she was more focussed on herself as she was "about to have a baby".
While admitting she understands "just as little about it then as I do now," she also said, "I've always been my sister's biggest supporter".
Britney Spears, however, has seen the interview with Jamie Lynn, and had some words to share with her followers on Twitter. While in bed after suffering from a high fever, the elder Spears sister said she "had to surrender to not caring" while watching the interview.
She continued that her sister is promoting a book "at my expense": "My sister said was that my behavior was out of control. She was never around me much 15 years ago at that time… so why are they even talking about that unless she wants to sell a book at my expense ??? REALLY?"
Spears also referenced the time that Jamie Lynn performed a mash-up of Britney's hits at the Disney Music Awards in 2017. Having previously shared her true feeling on the performance, she once again referenced this, adding that doing that performance herself was "everything I have ever wanted" while her sister "never had to work for anything".
She wrote: "I know it may sound like a silly thing to most people but I wrote a lot of my songs and my sister was the baby. She never had to work for anything. Everything was always given to her !!!!
"If you were me, you might understand asking for 13 years for remixes to go into a small venue show and on tours !!!! 13 years later they assign me as the MOTHER OF ALL… heart of gold … Britney sitting there seeing a 15 minute performance of everything I have ever wanted… But see, I always was the bigger person."
When Britney confronted her sister about it at the time, she said Jamie Lynn responded with "Well, it wasn’t my idea".
She added: "Hope your book does well, Jamie Lynn !!!!!"
UPDATE: Jamie Lynn has published a reaction to her sister's Twitter post. Taking to Instagram, the younger Spears sister writes: "Quite frankly, the things being said are absolutely not the truth, and I have to clarify that, because now it's getting harder for me to rationalize to my oldest daughter why our family continues to get death threats, as a result of their aunt's vague and accusatory posts, especially when we know she could tell the truth, and put an end to all of it if she wanted to."
The full post can be read here.