The actress explained that Cassie is too wary of jeopardising her friendship with Diana (Shelley Hennig) to pursue a romance with Adam (Thomas Dekker).
"It's an ongoing love triangle," Robertson told TV Guide. "It's a storyline that will be dragged out until the end of time.
"The relationship between Diana and Cassie is something that Cassie values more than anything, more than this crazy feeling towards Adam. Until the Adam-Diana thing completely fades away, or until it becomes something that is not a threat to Cassie's and DIana's relationship or friendship, I don't think you'll see much of Cassie and Adam."
However, Robertson teased that "there will be a few things here and there that will hint otherwise".
The Secret Circle airs on Thursdays at 9/8c on The CW in the US and on Wednesdays at 8pm on Sky Living in the UK.
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