Bynes, 27, is enrolled at the Orange County campus of Fashion Institute of Design and Merchandising. A source told E! she had planned to major in fashion design but then changed to merchandise project development.
Bynes spent six months in rehab last year, finishing up in December.
She began the year with a week at Miracle Fitness Retreat in Utah. Austan Torson, the owner, said Bynes wanted to get into shape and learn how to eat healthier food.
E! said her parents now drive her to a Los Angeles gym.
Bynes began acting at the age of 7 and had a busy career in both television and movies. She announced her retirement in 2010, changed her mind and then retired again in 2012.
Last year, she faced criminal charges including marijuana possession and reckless endangerment in New York City for allegedly throwing a bong out of her apartment window. On Jan. 10, her lawyer accepted a deal in which the charges will be dismissed if she stays out of trouble for six months.