The actress, who plays Roxy Mitchell in the BBC One soap, revealed that she sees Maslen - Roxy's on-off lover Jack Branning - as a brother, meaning intimate scenes can be uncomfortable.
"Scott's like my big brother and I absolutely freak out every time I have to kiss him. The director says, 'Action!' and we kiss, and then when he says, 'Cut!' we both hit and punch each other and he pushes me off him and I push him off me. We're like a pair of three-year-olds," Simons told the Sunday MIrror.
Roxy had a one-night stand with Jack two-and-a-half years ago behind sister Ronnie's (Samantha Womack) back, resulting in the birth of daughter Amy.
The pair rekindled their fling a few weeks ago when they enjoyed another night of passion in the run-up to their custody battle over Amy.
"The first time we got together was when we conceived Amy and back then I didn't know Scott very well, so it wasn't so strange," she continued. "When I read the script and realised we had to kiss I said, 'Oh my God - I can't believe we've got to kiss!'. Then Scott ran down from his dressing room and said exactly the same thing."
Roxy has since moved her affections to Jack's brother Max and will target Alfie Moon in an upcoming storyline.
"Sometimes it feels as though Roxy will go for anyone with a pulse. She's got very low self-esteem and likes anyone who pays her attention," Simons concluded.