It is her shortest style so far.
She debuted her new look on March 18 on "Late Night with Seth Meyers", reported Ace Showbiz.
After Meyers said the 21-year-old actress looked outstanding with her new short haircut, she thanked him and said she was premiering it on his show.
"Thank you so much, I'm premiering it right now on the show," she told Meyers.
The "This Is 40" star still did not explain why she cut her hair short.
Many people suggest that it may be for her role on "Girls" where she portrays Hannah Horvath. Others assume she may be going undercover on "Scandal".