'Pretty Wild' Star Heads into Court ... Then Jail

Neiers -- who pled no contest in May to the burglary of Orlando Bloom's home -- was sentenced to spend six months behind bars. Today, she is turning herself in to authorities to begin her sentence.

According to a detective's testimony back in December, Neiers admitted to being drunk the night of the burglary ... and said she threw up and peed in Orlando's bushes.

UPDATE 9:59 AM PT: The judge just ordered Alexis to spend 180 days behind bars -- as expected -- with 4 days credit. Her parents stood up and waved goodbye. Alexis will be heading to the women's jail in Lynwood, CA -- the same place Paris Hilton spent time behind bars in 2007.