The singer strikes a series of smouldering poses in the new ads and says it seemed fitting to lend her edgy look to her sister's country-inspired teen fashion brand.
Ashlee told People.com: ''[Jessica's] a bit more girly, and I kind of like to bring an edge to my looks. I do like to be in dresses, I just like to toughen it.
''I have a pretty cool sister with an amazing sense of style, and I was honored to get to do the shoot, we keep it in the family. Jessica's a fun one to work with.''
The two siblings - who both collaborated on the collection - appear to have mixed their contrasting styles in the first-look photos of the campaign.
Rocking an eclectic mix of a plaid shirt, flowery dress and chunky studded ankle boots, Ashlee champions her signature casual vibe.
Ashlee can also be seen wearing a short striped dress with knee-high boots and a maroon evening dress, which she admitted was her favourite piece.
Reminiscing about the desert photoshoot directed by Ellen von Unwerth, she said: ''We were all having a good time, kicking dirt in pretty dresses they did tell us to look for ticks! And I was like, 'Okay, I'm just going to roll in the dirt.''
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