The 28-year-old singer responded to critics in an Instagram post Monday following reports Britney was forced to seek treatment in a mental health facility.
Jamie Lynn shared a video from 2009 of herself and Britney being hounded by paparazzi. Jamie Lynn sticks up for Britney after a woman harasses the singer and tells her to leave the area.
"10 years ago, who was there?? I have been here long before anyone else, and I'll be here long after. I love my sister with everything I have. So, anyone or anything that speaks to the contrary can GTFOH with all the comments about what you don't understand," Jamie Lynn wrote.
"Do not come for me or the ones I love anymore. You can move the 'blank' outta here with all that, just like this other lady who was running her mouth," she said.
Page Six said Jamie Lynn has been inundated with comments from fans concerned about Britney. Many demanded Jamie Lynn "save Britney" and questioned whether she has the singer's best interests at heart.
"You should help your sister, that's the only reason why you are 'famous,'" one person wrote.
"#FreeBritney" trended on social media last week after an unnamed man, who claimed to be part of Britney's legal team, called into the Britney's Gram podcast and said Britney's father, Jamie Spears, was forcing the singer to get help.
Britney has been under a conservatorship, now solely run by her father, since 2008. She surprised fans in January by cancelling her Las Vegas residency to care for her dad following his emergency surgery.
E! News reported this month Britney had checked in to a mental health facility. The singer was spotted with her boyfriend, Sam Asghari, during an outing in Los Angeles on Easter Sunday.