Mary-Kate Olsen Back at School

By Liz McNeil and Natasha Stoynoff

10/25/2004 at 02:00 PM EDT

Mary-Kate Olsen returned to New York over the weekend, as she prepared to head back to school and joined sister Ashley for a trip to one of her favorite restaurants.

Olsen spokesman Michael Pagnotta confirms to PEOPLE that Mary-Kate "is back in town. She'll be back (in school). Ashley is here, too."

The teen stars marked Mary-Kate's return with a trip to one of her favorite spots, Next Door Nobu, for a late Sunday dinner, joined by Ashley, her new boyfriend, restaurateur Scott Sartiano, and an unidentified man. Mary-Kate, wearing black pants, a dark jacket and little red plastic Chinese slippers, put her hand on her sister's shoulder as they made their way towards the door at around 10:30 p.m. The group got into a black SUV and drove off.

Last week, Olsen returned to Southern California for a few days, and her rep shot down reports that she was leaving school at New York University to re-enter treatment for an eating disorder. (She went public with her battle over the summer.)

"She is in L.A. on personal business. She is not going back into treatment," Pagnotta said last week. "She has a team of people of both coasts whom she can access in L.A. or New York."