Former star Tori Spelling is fearing her husband Dean McDermott will cheat on her with a co-star, because the couple fell in love on-set while married to different people.The couple embarked on a steamy love affair during the filming of the TV movie "Mind Over Murder," while McDermott was still married to actress Mary Jo Eustace and Spelling was with Charlie Shanian.They wed in 2006, but Spelling admits she is anxious McDermott will repeat his on-set infidelity with another actress. She says, "Of course (I'm scared of that)! He told Jenny (Garth), 'Tori thinks I'm going to meet someone and run away with her, but I'm not.' It's just a girl thing, you just (let your mind) go there."