Mary-Kate Olsen headed back to her NYC apartment yesterday after running errands with her sister Ashley. Both girls are in the middle of jam-packed Summers — in addition to turning 24, they're busy expanding The Row and hitting the social scene. Mary-Kate was on the West Coast earlier this month, where she enjoyed a dinner date with a new man. After recently running into her ex Nate Lowman, it seems like she's moving on from their February split. Ashley, meanwhile, is focusing on business and going strong with her boyfriend Justin Bartha.