Sebastian Telfair's sister just fessed up in court and admitted to threatening to kill the ex-NBA star's estranged wife -- and now, she's facing up to 5 years in prison over it all.
Octavia Telfair had been arrested in May 2019 after federal investigators said she spewed vile threats toward Samantha Telfair.
Prosecutors claimed after Samantha had testified against Sebastian in his gun case ... Octavia felt it was all treacherous, called Samantha repeatedly and left terrifying threats.
Samantha told investigators that Octavia had told her she would "kill my kids and cut my face.