Jamie Lynn Spears

The letter demands that Jamie Lynn Spears stop 'publicly airing false or fantastic grievances' about her famous older sister.

Taking to Instagram, the younger Spears clapped back hard.

"I've faced my worst fear now," she says.

Eleven-year-old Maddie is fine, just appears she won't be exercising her wrist for a little while!

Britney shared some details in announcing her new Las Vegas Residency Domination has been scrapped.