The two are currently working as mentors on the series, which sees aspiring designers go head-to-head, but are said to have very different ideas about what they think looks good.
'They chat only when they need to, and they have wildly different opinions about style,' a source told Us Weekly.
'Nicole may know trends, but Jessica believes she knows how to make clothes for all kinds of women,' added a second insider, although other sources told the magazine that the ladies 'get along well, and hang out on set.'