When Mark Fuhrman lied about using the N word in the Simpson case it was a huge deal. The case died and he was convicted of a felony. Rachel admittedly lies under oath and it is no big deal. Even the defense did not make a big deal over her lying. And she said she lied because Sabrina Fulton was present. Guess what, Sabrina was there when she testified in court.
Aside from homicide crimes, duress is normally an available defense; so prosecuting Jeantel wouldn’t get a conviction, and be a waste of prosecutorial resources.
You assume Fuhrman lied. He denied another witness’s claim that he used the N word and also allegedly said that he thought all blacks should be burned in a bonfire.