Britney Spears is not holding back.

In the months since her conservatorship ended, questions have arisen as to who in the pop star's life contributed to — and benefited from — the legal guardianship.

Among those being brought into question is the "Toxic" singer's sister Jamie Lynn Spears, who is now an actress and country singer-songwriter. Jamie Lynn, 30, has expressed support for her sister on social media, but Spears, 40, has jabbed her family multiple times, even name-dropping Jamie Lynn on a number of occasions.

In a lengthy statement she shared on Twitter Thursday, Spears tore into Jamie Lynn as the star promotes her upcoming book, all while recounting a health scare  from the previous night.

JAMIE LYNN SPEARS DESCRIBES ALLEGED INCIDENT WHERE SISTER BRITNEY 'GOT IN HER FACE' WITH HER DAUGHTERS PRESENT

In her message, Spears said she "got really sick last night" with a fever of 104 degrees. She said she asked security to retrieve pain medication to treat a headache but was told that security cannot leave the property.

Britney Spears and sister Jamie Lynn Spears

Britney Spears slammed her sister Jamie Lynn over an interview she gave to promote her upcoming book. (Image Group LA/Disney Channel via Getty Images)

The singer said that her 104-degree fever amounted to an emergency and railed against the "sarcasm" in the security guard's voice when he declined her request.

The star said she then turned her attention to an interview that Jamie Lynn gave to promote her book.

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"I watched it with a 104° fever lol and it was actually kind of nice having a fever so high cause I had to surrender to not caring," the singer wrote. "I just couldn't give a f--k but my head hurt so bad."

The star said there were two things in particular that bothered her about her sister's interview, one being when the "Zoey 101" alum said Spears' "behavior was out of control," as Spears put it.

Jamie Lynn Spears

Spears said her sister Jamie Lynn "never had to work for anything" and performed remixes of the pop star's song at someone else's suggestion. (Image Group LA/Disney Channel via Getty Images)

"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 wrote.

Spears also pointed to her sister being asked about performing remixes of Spears' songs, something the pop star has aired grievances over before.

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"I know it may sound like a silly thing to most people but I wrote a lot of my songs and my sister was a baby. She never had to work for anything. Everything was always given to her !!!!," Spears explained. "If you were me, you might understand asking for 13 years for remixes to go into a small venue show and on tours !!!!"

She continued: "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. They all got to DO IT and PLAY ME and I always sat there and took it."

Now, however, Spears said that asking for "what was just given to" Jamie Lynn is "the last thing I would ever do."

"So yes, they did ruin my dreams," Spears said. "I do remember asking my sister why she did that when she knew I was waiting to change my show and her only words were ‘Well, it wasn’t my idea'… Hope your book does well, Jamie Lynn !!!!"

The star then said she'd be taking a hiatus from Instagram for a time, as the media and "this business has always been extremely hateful to me."

BRITNEY SPEARS AND JAMIE LYNN SPEARS FEUD: EVERYTHING TO KNOW

"I've given enough … MORE than enough. I was never given back ever what I want," Spears added. "They say in the bible ‘ask and you shall receive’ …. uhhhhh not in my life … just like my family, I asked security for Aleve as I laid there with 104 degree fever in bed and he told me NO !!!!"

"My family ruined my dreams 100 billion percent and try to make me look like the crazy one while I have a 104° fever, not being able to move in my bed !!!!" she added. "My family loves to pull me down and hurt me always so I am disgusted with them !!!!"

Britney Spears

Britney Spears has been very open about her anger toward her family since her conservatorship ended last year. (Steve Jennings/WireImage)

The star explained that while her fever has dropped to 101 degrees, her head feels like "two basketballs because it's sore from the fever" and her throat is sore.

"… The last thing I will ever ask to see in my life is a doctor," she said, seemingly in reference to previous comments about being forced into taking unwanted medications. "I mean would you if you were me ???? JUST SAYING !!!!"

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Elsewhere in the statement, Spears described other symptoms she experienced like having "chill bumps everywhere, like I was freezing" despite high body temperatures and skin that was extremely sensitive to the touch.

Spears concluded: "Psss lesson learned from all this don't trust people or anyone … make your cats and dogs your family and take care of your own damn self !!!!"

In a follow-up tweet, Spears noted that her fiancé Sam Asghari got her medicine, "Pssss my fiancé got my medicine ... I survived !!!!" she stated.

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Reps for Britney and Jamie Lynn did not immediately respond to Fox News' request for comment.