She reported Tuesday morning, a few weeks early, for a three year sentence.
RELATED: Actress Lori Loughlin reports to California prison after plea in college admissions scandal
It's for her role in recruiting women into NXIVM as sex slaves.
The group's founder is serving a 120 year prison sentence.
Mack is at the same federal prison where actresses Lori Laughlin and Felicity Huffman recently served time for their roles in the college admissions scandal.