"This time it's bohemian Americana, so that was the theme," Ashlee explained of Jessica's collection. "And she asked me to shoot the campaign which was an honor and she was there directing it."
According to their mother, Tina, it made sense for Ashlee to serve as the model for the campaign because she has "more of an edge" than her sister.
"Both girls are all-American, but Ashlee has more of an edge," Tina explained. "Jessica is a little more ... like sweet Americana—that's the difference."
Asked about which path Jessica's 14-month-old daughter Maxwell might be leaning toward, Tina said "she's already going to be a lot like Ashlee."
On Tuesday, Jessica hosted the public launch of her new fall line at Above Allen in New York City. While speaking to reporters at the event, her sister Ashlee explained she had a blast while shooting the campaign for the collection.
"We were all having a good time, kicking dirt in pretty dresses. They did tell us to look for ticks! And I was like, 'OK, I'm just going to roll in the dirt," she said.
Notable deaths of 2014 [PHOTOS]